CANBERRA, March 24 -- Evidence is mounting of a trail of possible wreckage from Malaysia Airlines flight MH370 but nothing can be certain until searchers retrieve an object that provides incontrovertible proof, an Australian expert said Monday.

"It's not a cohesive picture just yet," Dr John Blaxland, senior fellow of the Strategic and Defence Studies Centre, Australian National University, said after a Chinese air crew announced they had seen new objects floating in the waters of the search area in the Southern Indian Ocean.

"Now this is encouraging news, but once again we need to be sober in judgement on this and wait till the facts are clearly established before we jump to any conclusions," said Blaxland.

"The problem is that we haven't been able to physically locate any of these items yet and pick them up out of the water and verify where they're from and what they are," he said.

"The picture is becoming more positive. There is increasingly a corroboration of facts and details about what we're seeing, but it 's not yet conclusive."

OTHER EXPLANATIONS

The arrival of more ships in the area would help with the chances of retrieving any of the objects spotted from the air, such as the wooden pallet, straps and other objects seen on Saturday, he said.

"A ship is actually pretty well placed because a pallet will actually bob in the water. It will actually break the surface of the water and there's quite a lot of people on the ship who are actually scouting out, looking out from the gunnels of the ship, looking out to sea," he said.

"And the ship is actually quite high so it's well placed to see for quite some distance."

He said there were a number of possible explanations for the objects sighted in satellite photos from the United States, China and France and for those sighted in air searches.

"At this stage it's just speculation as to what it might be. We can only hope that the correlation of the bits of information will prove conclusively one way or the other whether we have MH370 identified," said Blaxland.

"We may well be on the cusp of actually getting our hands onto an item that confirms one way or the other whether we have identified MH370. If we do confirm that this is MH370, that is a very significant breakthrough."

SUBSTANTIAL TASK

Any objects positively identified as coming from MH370 would allow searches to calculate a "splash point" based on currents and other factors and begin the task of finding the black box data and cockpit voice recorders vital to solving the mystery.

"Then we've got a recovery task that is a pretty substantial task -- it is one that is beyond the capabilities of most countries," said Blaxland.

"The one country that is best equipped to do that is the United States with the equipment of the United States Navy. They have done this kind of work before."

Once a precise crash area is identified, the technology to find the black box could be in position quickly.

"At the moment we still have about a week's worth of battery life to go, so it will be honing in on that signal initially. That signal will act like a beacon for the recovery for the unaccompanied or unmanned submersible vehicle that will be conducting the search and then there are automatic mechanisms to basically get the black box," Blaxland added.