Story highlights A Chinese ship picked up a signal on Friday and Saturday, authorities say

An Australian naval vessel is pursuing a more recent detection in a separate location

An official calls the sounds "an important and encouraging lead" but urges caution

Up to 10 military planes, two civil aircraft,13 ships will assist in Sunday's search

Search teams looking for Malaysia Airlines Flight 370 are investigating a number of sounds detected by ships in the southern Indian Ocean, authorities said Sunday, but it's not yet clear if any of them are from the missing plane's so-called black box.

A British Royal Navy vessel is on its way to an area where a Chinese ship reported picking up electronic signals twice, once on Friday and again on Saturday, said Angus Houston, the head of the Australian agency coordinating search operations.

And the Australian naval ship Ocean Shield, which has highly sophisticated equipment, is pursuing "an acoustic noise" that it detected in a different area, Houston said at a news conference.

He said the detections were "an important and encouraging lead," but he cautioned that they be treated "carefully" as they haven't been verified as being related to Flight 370.

Fevered search

Searchers are desperately seeking any clue about the location of the airliner that disappeared nearly a month ago with 239 people on board.

Up to 10 military planes, two civil aircraft and 13 ships will assist in Sunday's search for the airline. The Australian Maritime Safety Authority (AMSA) plans to search three separate areas Sunday about 2,000 kilometers (about 1,240 miles) northwest of Perth. That area totals about 216,000 square kilometers (83,000 square miles).

Australian planes are being deployed to the area where the Chinese ship, Haixun 01, picked up signals that would be consistent with those emitted by an aircraft's flight recorders, said Houston, the chief coordinator of Australia's Joint Agency Coordination Centre.

A number of white objects were sighted about 56 miles (90 kilometers) away from where the sound was detected, he said.

But he stressed that were was so far no confirmation that the signals and objects are related to Flight 370.

"In the days, weeks and possibly months ahead, there may be leads such as the one I'm reporting to you this morning on a regular basis," Houston, a retired air chief marshal, said.

Handheld hydrophone

Video on Chinese state-run CCTV shot Saturday shows crew members from the Haixun 01 boarding a small yellow dinghy and using what appears to be a handheld hydrophone. The three men on board lower the device into the water on a pole.

The handheld ping-locating technology used by the Chinese ship is not as versatile as a U.S. Navy towed locator, which goes as deep as 20,000 feet, far from surface noise, according to experts.

The U.S. Navy hydrophone -- or underwater microphone, is on board the Australian ship Ocean Shield, which recently joined the search for Flight 370.

The state-run Chinese news agency, Xinhua, said a detector deployed by the Haixun 01 patrol ship picked up the signal around 25 degrees south latitude and 101 degrees east longitude.

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That puts it about 1,020 miles (1,640 kilometers) west-northwest of Perth, Australia, between current and previous search zones, and about 220 miles (354 kilometers) south of the closest of the three areas searched Saturday, said Judson Jones, a meteorologist with CNN International.

Houston said Sunday that the sounds were detected "in the high probability area."

White objects spotted

Also found Saturday -- spotted by a Chinese air force search plane -- were white objects floating near the search area.

Investigators have failed to link any of the many previous sightings of debris to the missing plane. But the proximity of the two finds raised hopes that this time might be different.

The ship first detected a signal Friday but couldn't record it because the signal stopped abruptly, a Shanghai-based Communist Party newspaper said. The signal detected Saturday, the Jiefang Daily said, occurred at 3:57 p.m. Beijing time (3:57 a.m. ET) and lasted about a minute and a half. It was not clear whether the signal had anything to do with the missing plane.

A China Central Television correspondent aboard the Haixun-01 (pronounced "high shuen") reported that the 37.5 kHz signal was detected for a minute and a half.

Fleeting acoustic

Houston confirmed the two separate detections and said they showed "some promise."

But the signals picked up by the Chinese searchers were "fleeting acoustic events," he said. "It's not a continuous transmission. If you get close to the device, we should be receiving it for a longer period of time."

The signal "is the standard beacon frequency" for the plane's cockpit voice recorder and the flight data recorder, said Anish Patel, president of pinger manufacturer Dukane Seacom.

"They're identical."

The frequency was chosen for use in the recorders "to give that standout quality that does not get interfered with by the background noise that readily occurs in the ocean."

Photos: The search for MH370 Photos: The search for MH370 Two years after Malaysia Airlines Flight 370 went missing, a relative of one of the passengers burns incense in Beijing on March 8, 2016. Flight 370 vanished on March 8, 2014, as it flew from Kuala Lumpur, Malaysia, to Beijing. There were 239 people on board. Hide Caption 1 of 43 Photos: The search for MH370 On July 29, police carry a piece of debris on Reunion Island, a French territory in the Indian Ocean. A week later, authorities confirmed that the debris was from the missing flight. Hide Caption 2 of 43 Photos: The search for MH370 Staff members with the Australian Transport Safety Bureau examine a piece of aircraft debris at their laboratory in Canberra, Australia, on July 20. The flap was found in June by residents on Pemba Island off the coast of Tanzania, and officials had said it was highly likely to have come from Flight 370. Experts at the Australian Transport Safety Bureau, which is heading up the search for the plane, confirmed that the part was indeed from the missing aircraft. Hide Caption 3 of 43 Photos: The search for MH370 In late February, American tourist Blaine Gibson found a piece of plane debris off Mozambique, a discovery that renewed hope of solving the mystery of the missing flight. The piece measured 35 inches by 22 inches. A U.S. official said it was likely the wreckage came from a Boeing 777, which MH370 was. Hide Caption 4 of 43 Photos: The search for MH370 Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on February 12, 2015. Protesters had demanded that the airline withdraw the statement that all 239 people aboard the plane were dead. Hide Caption 5 of 43 Photos: The search for MH370 A police officer watches a couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane. Hide Caption 6 of 43 Photos: The search for MH370 Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public. Hide Caption 7 of 43 Photos: The search for MH370 Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014. Hide Caption 8 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014. Hide Caption 9 of 43 Photos: The search for MH370 The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014. Hide Caption 10 of 43 Photos: The search for MH370 A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014. Hide Caption 11 of 43 Photos: The search for MH370 A relative of a missing passenger cries at a vigil in Beijing on April 8, 2014. Hide Caption 12 of 43 Photos: The search for MH370 Australian Defense Force divers scan the water for debris in the southern Indian Ocean on April 7, 2014. Hide Caption 13 of 43 Photos: The search for MH370 A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014. Hide Caption 14 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014. Hide Caption 15 of 43 Photos: The search for MH370 On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370. Hide Caption 16 of 43 Photos: The search for MH370 The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions. Hide Caption 17 of 43 Photos: The search for MH370 A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014. Hide Caption 18 of 43 Photos: The search for MH370 Flight Lt. Jayson Nichols looks at a map aboard a Royal Australian Air Force aircraft during a search on March 27, 2014. Hide Caption 19 of 43 Photos: The search for MH370 People in Kuala Lumpur light candles during a ceremony held for the missing flight's passengers on March 27, 2014. Hide Caption 20 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived." Hide Caption 21 of 43 Photos: The search for MH370 Grieving relatives of missing passengers leave a hotel in Beijing on March 24, 2014. Hide Caption 22 of 43 Photos: The search for MH370 A passenger views a weather map in the departures terminal of Kuala Lumpur International Airport on March 22, 2014. Hide Caption 23 of 43 Photos: The search for MH370 A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia. Hide Caption 24 of 43 Photos: The search for MH370 Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search. Hide Caption 25 of 43 Photos: The search for MH370 Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight. Hide Caption 26 of 43 Photos: The search for MH370 A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014. Hide Caption 27 of 43 Photos: The search for MH370 On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet. Hide Caption 28 of 43 Photos: The search for MH370 U.S. Navy crew members assist in search-and-rescue operations in the Indian Ocean on March 16, 2014. Hide Caption 29 of 43 Photos: The search for MH370 Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean. Hide Caption 30 of 43 Photos: The search for MH370 A Vietnamese military official looks out an aircraft window during search operations March 13, 2014. Hide Caption 31 of 43 Photos: The search for MH370 Malaysian air force members look for debris near Kuala Lumpur on March 13, 2014. Hide Caption 32 of 43 Photos: The search for MH370 Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014. Hide Caption 33 of 43 Photos: The search for MH370 A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014. Hide Caption 34 of 43 Photos: The search for MH370 A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported on March 8, 2014. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10, 2014. Hide Caption 35 of 43 Photos: The search for MH370 A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand. Hide Caption 36 of 43 Photos: The search for MH370 Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9, 2014. Hide Caption 37 of 43 Photos: The search for MH370 Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014. Hide Caption 38 of 43 Photos: The search for MH370 The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014. Hide Caption 39 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8, 2014. Hide Caption 40 of 43 Photos: The search for MH370 A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014. Hide Caption 41 of 43 Photos: The search for MH370 Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014. Hide Caption 42 of 43 Photos: The search for MH370 Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said. Hide Caption 43 of 43

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But he said he would like to see more evidence. "I'd like to see some additional assets on site quickly -- maybe some sonobuoys," he said, referring to 5-inch-long sonar systems that are dropped from aircraft or ships.

And he said he was puzzled that only one signal had been detected, since each of the recorders was equipped with a pinger, which is also called a beacon.

No confirmation

Other experts cautioned that no confirmation had been made that the signal was linked to the missing plane.

"It ought to be easy to rule it in or rule it out, and they ought to go do it," said Mary Schiavo, a CNN aviation analyst and a former inspector general for the U.S. Department of Transportation.

Saturday's leads came as concern was rising that the batteries powering the missing Boeing 777's locator pingers would soon go dead. The plane disappeared on March 8; its batteries were guaranteed to work for 30 days underwater, and are predicted to die slowly over the following days. Monday marks day 30.

The batteries on Flight 370's black boxes were due to be replaced in June, the Malaysia Airlines chief executive said Saturday.

"We can confirm there is a maintenance program. Batteries are replaced prior to expiration," Ahmad Jauhari Yahya said.

Relative reacts

The tentative nature of the first report of an acoustic signal was not lost on one Chinese relative of one of those aboard. "There is not confirmation, and we are all waiting patiently," the relative told CNN Producer Judy Kwon in a text message.

Still, Malaysia's acting transport minister, Hishammuddin Hussein, was sanguine: "Another night of hope-praying hard," he tweeted in response to the initial detection.

"We've had a lot of red herrings, hyperbole on this whole search," said oceanographer Simon Boxall, a lecturer in ocean and earth science at the University of Southampton. "I'd really like to see this data confirmed."

If this proves to be what investigators have been searching for, "then the possibility of recovering the plane -- or at least the black boxes -- goes from being one in a million to almost certain," he said.

But, he added, "It could be a false signal."

CNN aviation analyst David Soucie was less skeptical. "This is a pinger," the airplane accident investigator said. "I've been doing this a lot of years, and I can't think of anything else it could be."