Three distinct but fleeting sounds have now been heard from the depths of the Indian Ocean, but authorities are still uncertain whether any of them are signals from the data recorder of the missing Malaysian passenger jet.
An Australian ship with sophisticated deep-sea sound equipment picked up a signal Sunday that could be from the Boeing 777's black box that tracks flight information. That followed sounds heard by a Chinese ship on both Friday and Saturday in a different section of the search area.
The head of Malaysia's civil aviation agency, Azharuddin Abdul Rahman, said authorities are hopeful the signals might prove to be a breakthrough in the search for the plane that disappeared nearly a month ago with 239 people aboard on a flight from Kuala Lumpur to Beijing. But a link to the aircraft has yet to be confirmed.
"Of course, we're going to hope for the best, but then everything needs to be confirmed, needs to be verified," Rahman said. "So we're not saying 'That's it,' you know. Still have to be verified."
Earlier, the head of the multi-national search for the jet, retired Australian Air Chief Marshal Angus Houston, told a news conference that although the pulses heard by the Chinese are consistent with a plane's black box flight recorder, officials cannot verify any connection at this stage between the signals and the Malaysian jet.
"This is an important and encouraging lead but one which I urge you to continue to treat carefully," he said. "We are working in a very big ocean and within a very large search area. And, so far, since the aircraft went missing we've had very few leads which allow us to narrow the search area."
◆ New Search Area
The potential breakthrough, however, the retired Australian air force chief confirms, is prompting the diversion of ships and planes to the area where the Chinese patrol vessel Haixun-01 detected acoustic pulses on Friday and Saturday in waters up to 4.5 kilometers deep.
Houston said, "At the moment, the data we have does not provide a means of verification. We have to do further investigation on the site itself."
Signals on a frequency of 37.5 kilohertz were detected two kilometers apart by the Chinese ship.
Authorities say an Australian vessel, the Ocean Shield, several hundred kilometers away and carrying a sophisticated U.S. Navy pinger locator, also heard a faint signal on the same frequency. It is to listen for more underwater sounds at its current location before heading to the spot where the Chinese patrol ship's hydrophone detected something.
A British Royal Navy vessel, the HMS Echo, last week detected a similar signal that turned out to be false.
The batteries for the locator beacon of the missing plane's black box are due to run out at any time.
◆ Nothing Found Yet
So far, all sightings of debris in the southern Indian Ocean have been determined to not be from the missing Boeing 777.
A dozen planes and 13 ships are continuing to search.
The Malaysia Airlines jet veered off course after departing Kuala Lumpur on a scheduled flight to Beijing on March 8. It was carrying 227 passengers -- mostly Chinese -- plus a crew of 12.
Investigators say they do not know whether the plane was hijacked or otherwise deliberately diverted by one of the two pilots.
Mechanical problems have not been eliminated as a cause, but investigators say they believe the plane's flight management system was re-programmed. After the plane's transponder was shut off, the jet turned back towards Malaysia and then stayed in an established flight corridor.
An analysis of routine pings from the engines to a satellite led investigators to conclude the aircraft ran out of fuel over the southern India Ocean.