An Australian navy ship in the Indian Ocean has detected signals that are consistent with those from an airplane's black box. Authorities say it is their "most promising" lead so far in the search for the missing Malaysia Airlines flight 370.

The ship is towing a device called a pinger locator, which detected two signals on Monday. The first lasted two hours and 20 minutes, and the second lasted for 13 minutes. On the latter, two distinct signals were audible, which would be consistent with a flight data recorder and a cockpit voice recorder, said Malaysia's Minister of Defense Hishammuddin Hussein.

"We've got a visual indication on a screen, and we've also got an audible signal. And the audible signal sounds to me just like an emergency locator beacon," said retired Air Chief Marshal Angus Houston, according to CNN. "We are encouraged that we are very close to where we need to be."

The chief coordinator of the Joint Agency Coordination Center retired Chief Air Marshall Angus Houston shows a map to the media during a press conference about the on going search operations for wreckage and debris of missing Malaysia Airlines Flight 370 in Perth, Australia, Monday, April 7, 2014.

This discovery comes just one day after a Chinese ship detected a pulse signal with a frequency of 37.5 kHz — the same frequency that black boxes use.

The signals detected by both ships are located about 1,100 miles from Perth — far enough away from land to assure authorities that the signals are from a man-made device — in an area of the ocean that is about 14,800 feet deep.

This image provided by the Joint Agency Coordination Centre on Monday, April 7, 2014, shows a map indicating the locations of search vessels looking for signs of the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. Image: Joint Agency Coordination Centre/Associated Press

However, officials say it could take days before they can confirm if the signals are from flight 370. After a month of false leads, authorities are still skeptical. Though they say this particular clue is promising, it's still unconfirmed that it's from the missing Boeing 777 that was carrying 239 people.

"Authorities must be cautious about unconfirmed findings and making conclusions," Hussein said at a news conference Monday. "We are cautiously hopeful that there will be a positive development in the next few days, if not hours."

Towed pinger locator deployed from HMAS Ocean Shield has detected signals consistent w/ those emitted by black boxes #MH370 @HishammuddinH2O — H2O Comms (@H2OComms) April 7, 2014

Despite all this, We are cautiously hopeful that there will be positive developments in the next few days #MH370 @HishammuddinH2O — H2O Comms (@H2OComms) April 7, 2014

The search to find the plane's black box is running out of time. Batteries in the flight recorders last only 30 days. As of Monday, the plane has been missing for 31 days. If the black box signal disappears before officials locate it, we may never know what happened to flight 370.

Additional reporting by Brian Ries