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. 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. We are working in a very big ocean and within a very large search area, and so far, since the aircraft went missing, we have had very few leads which allow us to narrow the search area."
The search has become more intense as the batteries in the plane's black box are due soon to reach the end of their life.
Ships using submersible sonar and numerous military and private aircraft were deployed Saturday in a patch of the Indian Ocean about 1,700 kilometers northwest of Perth, Australia. Position information given out by China indicates its search ship was slightly outside the targeted area when it monitored the "ping" signal.
The Boeing 777 vanished without any distress calls, and authorities have refused to rule out any possibilities, including hijacking, sabotage or a mechanical malfunction. Malaysian officials say they are continuing to investigate whether any deliberate action by the pilots or crew could have sent the plane down.