Crew members look outside windows from a Malaysian air force CN235 aircraft during a search-and-rescue operation to find the missing Malaysia Airlines Flight 370 over the Strait of Malacca. Prime Minister Najib Razak said on Saturday that Malaysia was ending its search for the vanished jetliner in the South China Sea after investigations indicated the missing plane likely turned far to the west.

March 15, 2014 Crew members look outside windows from a Malaysian air force CN235 aircraft during a search-and-rescue operation to find the missing Malaysia Airlines Flight 370 over the Strait of Malacca. Prime Minister Najib Razak said on Saturday that Malaysia was ending its search for the vanished jetliner in the South China Sea after investigations indicated the missing plane likely turned far to the west. Mohd Rasfan/AFP/Getty Images

In the most comprehensive account to date of the missing Malaysia Airlines Flight 370’s fate, Malaysian Prime Minister Najib Razak on Saturday said that the plane was steered off course after its communications systems were intentionally disabled and that it could have flown for seven additional hours.

An international hunt for clues in the disappearance of a Malaysia Airlines passenger jet intensified, with dozens of ships searching a vast expanse of sea and investigators chasing down leads. But authorities acknowledged that they were stymied.

An international hunt for clues in the disappearance of a Malaysia Airlines passenger jet intensified, with dozens of ships searching a vast expanse of sea and investigators chasing down leads. But authorities acknowledged that they were stymied.

As the search pressed on for a vanished Malaysian airliner, military officials said radar data showed that it inexplicably turned and headed toward the Malacca Strait, hundreds of miles off its scheduled flight path, news agencies and Malaysian media reported.

Gen. Rodzali Daud, Malaysia’s air force chief, was quoted by the Malaysian newspaper Berita Harian as saying that the Boeing 777 jet was detected by military radar at 2:40 a.m. Saturday near Pulau Perak at the northern end of the strait, which separates the western side of the Malaysian peninsula from the Indonesian island of Sumatra.

“After that, the signal from the plane was lost,” he told the newspaper.

Military officials, speaking to the Associated Press and Reuters, confirmed the air force chief’s remarks. On Wednesday morning, however, Daud took them back, denying he had ever made such a statement, although he reiterated that the military has not “ruled out the possibility” that the plane turned back.

The confusion about Malaysian military thinking came after four days of searching for the vanished jet and indicated a degree of chaos in the operation, which is being coordinated by Malaysia’s civil aviation department. Separately, Malaysia Airlines said Tuesday that the plane could have been trying to turn back to Subang, an airport on the northern outskirts of Kuala Lumpur.

A senior official at Malaysia’s civil aviation department, requesting anonymity because he was no authorized to speak with the press, said it was possible the jet had tacked westward based on the military’s radar plot, but that the data was not conclusive.

“We need an expert from the FAA in determining whether this information is genuine,” the senior official said, referencing the U.S. Federal Aviation Administration. He said Malaysian authorities were meeting Wednesday to discuss the next steps.

Although search teams from 10 nations have combed both sides of the Malaysian peninsula for evidence of wreckage, authorities until now had indicated that the plane probably was in the Gulf of Thailand, where it disappeared from civilian radar shortly after taking off from Kuala Lumpur en route to Beijing.

“If I was out there with a team, on a boat, working day and night, and then to have someone tell you, ‘Oh, guess what, we don’t think it’s here after all. It might be 500 miles away.’ Wow,” said David Gallo, director of special projects at Woods Hole Oceanographic Institution, who co-led the successful search for Air France Flight 447, which vanished in 2009 over the Atlantic.

The reports that Flight MH370 veered so far off course added a bizarre and confusing new element to a case that has baffled investigators. Some aviation experts said the search might need to be further expanded. Given the fuel it had, the plane could have made it as far as India.

In the latest signal of impatience from Beijing, the Chinese military sent two additional aircraft to help with the search Tuesday, and it deployed three more vessels, which are expected to arrive in the area by Wednesday morning, according to state-controlled Xinhua News Agency. Japan also said it would dispatch a disaster relief team.

Vietnam said Wednesday that it was scaling back the search in its waters. According to Reuters, Pham Quy Tieu, the deputy transport minister, told reporters that he’d asked Malaysia for more information about whether the jet had changed course after vanishing from civilian radar, but that he hadn’t received any response.

View Graphic Flight mystery deepens

Four days after the plane carrying 227 passengers disappeared, investigators acknowledged that they still were mystified by what happened on board. Malaysian authorities said they continued to look for signs of sabotage or hijacking but also were considering the possibility of psychological or personal problems among the passengers or crew.

They played down any connection between the plane’s fate and two Iranian passengers who had boarded the aircraft with stolen Austrian and Italian passports.

“The more information we get, the more we are inclined to conclude it is not a terrorist incident,” Ronald Noble, secretary general of the international police agency Interpol, told reporters.

But in Washington, CIA Director John Brennan said terrorism could not be ruled out, while stressing that authorities have reached no conclusions about what caused the plane’s disappearance.

“It’s still a mystery at this point,” Brennan said after delivering a speech in Washington.

Reuters, citing an unidentified Malaysian military source, said military radar picked up the plane as it crossed the Malaysian peninsula in what were apparently its final minutes of flight. Malaysian media reported that some residents spotted a plane flying low, near the city of Kota Bharu.

If the reports were correct, it was unclear why many authorities didn’t appear aware of the information earlier in the investigation. Authorities have consistently said that Flight MH370’s transponder signal — which communicates with civil aviation radar — abruptly stopped at the time the plane was supposed to be entering Vietnamese air space. But military radar could have continued to track the aircraft.

If the plane dropped from a low altitude into the Malacca Strait, it might explain the lack of a major debris field. Malaysia Airlines said in a statement early Tuesday that the western coast of Malaysia was “now the focus” of the search. But a spokeswoman for the airline later said that the wording was a mistake and that there was no emphasis on any location.

Malaysian civil aviation chief Azharuddin Abdul Rahman said searches were continuing “on both sides” of the peninsula.

The discovery of two passengers with stolen documents had raised alarm that a terrorist attack might have brought down the plane. But authorities said Tuesday that the two Iranians carrying stolen passports — Pouria Nour Mohammad Mehrdad, 19, and Delavar Seyed Mohammad Reza, 29 — did not appear to be linked to any violent group. Both arrived in Malaysia the same day, Feb. 28, officials said.

At a news conference in Kuala Lumpur, Khalid Abu Bakar, inspector general of Malaysia’s police, said that the 19-year-old was trying to migrate to Germany: His mother had been waiting for him in Frankfurt, then called Malaysian authorities when he did not show up. Interpol identified the other Iranian at a separate news conference, although his reasons for traveling were not immediately clear. While Malaysia might seem an odd stop for Middle Eastern men heading to Europe, it is relatively easy for Iranians to enter the country, and airline tickets to reach the Southeast Asian country are fairly cheap.

Khalid said that Malaysia has been examining images of baggage, studying closed-circuit monitors for suspicious behavior at the airport terminal and trying to obtain photos and profiles of the passengers.

Search teams, meanwhile, battled wind and whitecaps while looking for any sign of debris from the plane, especially wreckage containing the crucial cockpit recorders. The instruments usually emit tracking signals for about 30 days.

The United States is using P-3 Orion surveillance aircraft and helicopters that fly just 500 feet above the water and depend on crews to spot potential debris.

With the surveillance aircraft, “the software that goes with the radar is smart enough to cancel out those waves,” Cmdr. William Marks, a spokesman for the U.S. Navy’s 7th Fleet, said in a phone interview from the Gulf of Thailand. “However, if you’re just using your eyeballs, it is a significant challenge, because the water is not flat any more.”

Denyer reported from Beijing. Jason Rezaian in Tehran; William Branigin, Ashley Halsey and Greg Miller in Washington; and William Wan, Liu Liu, Gu Jinglu and Xu Jing in Beijing contributed to this report.