The head of the multinational search for the missing Malaysian jetliner says that an Australian ship detected an 'acoustic event' early Sunday morning and that a Chinese ship has reported a second pulse consistent with an aircraft black box in a different location, though the Chinese reports could not be verified.

Australian Air Chief Marshal Angus Houston said that Ocean Shield, an Australian vessel, is closely investigating a stretch of the southern Indian Ocean after picking up an acoustic occurrence.

Angus called it an encouraging development but cautioned that very little is currently known about the nature of the transmission.

He also said that Chinese authorities have told Australian officials that Haixun 01, the ship that on Friday reportedly picked up an electronic pulse at 37.5 kilohertz (thousands of cycles per second) — the same frequency emitted by flight data recorders — detected a series of pulses that lasted approximately 90 seconds on Saturday afternoon.

The pulses were heard about 2 kilometres from the previous signal that Haixun 01 reported. Australian ship Echo and multiple airplanes are on their way to assist Haixun 01 search that area, while Ocean Shield will move to the location of those reported pulses if nothing comes of the 'acoustic event' it picked up Sunday morning.

"Ocean Shield is in the process of exploiting another acoustic event that we need to look into to determine if there's anything to it. This is a painstaking process and if we get any leads whatsoever, we investigate them," Angus said.

Australian ship Ocean Shield detected an 'acoustic event' on Sunday morning. If the vessel's investigation of the occurrence does not turn up any new leads, it will head south to assist the Chinese ship Haixun 01 in its search.

According to Angus, the international investigative team has also concluded that their original interpretation of satellite flight path data underestimated the speed of the jet, and that it may have travelled farther south than previously believed. The southern region of the search area — where Haixun 01 is currently operating in waters about 4,500 metres deep — will now be more heavily prioritized.

Because the pinger locator can pick up signals to a depth of 6,100 metres, it should be able to hear the plane's data recorders even if they are in the deepest part of the search zone — about 5,800 metres. But that's only if the locator gets within range of the black boxes — a tough task, given the size of the search area and the fact that the pinger locator must be dragged slowly through the water at just a few kilometres per hour.

If the signals detected by Haixun 01 are confirmed, it will take a "long period of time" to recover the black boxes, Angus said,

"That's incredibly deep, Four and a half kilometres, straight down. Any recovery operation is going to be incredibly challenging."(CBC News)