Officials searching for the missing Malaysia Airlines plane say material has washed ashore off the coast of Western Australia.

The Australian Transport Safety Bureau (ATSB) is now examining photographs of the objects, which have been secured by police in the region, to establish whether they are linked to flight MH370.

Authorities said the images had also been passed to investigators in Malaysia. The development came after Australia pledged to keep searching for the plane despite no sign of wreckage after almost seven weeks.

Bad weather is continuing to hamper the search with aircraft grounded for the second day due to heavy rain, low clouds and rough seas.

An undersea drone is nearing the end of its first full mission and Australian Prime Minister Tony Abbott says the search strategy may change if seabed scans taken by the US Navy drone fails to find a trace of MH370, which vanished on March 8th with 239 people on board.

"We may well re-think the search but we will not rest until we have done everything we can to solve this mystery" he said.

"The only way we can get to the bottom of this is to keep searching the probable impact zone until we find something or until we have searched it as thoroughly as human ingenuity allows at this time"

Over 80% of search zone covered

The Bluefin-21 drone is a key component in the search after the detection of audio signals, or "pings", believed to be from the plane's black box flight .

The search co-ordination centre said the robotic submarine had so far covered more than 80% of the 310 square kilometre seabed search zone off the Australian west coast, creating a three-dimensional sonar map of the ocean floor, but failing to find anything of interest.

The 4.5-kilometre deep search area is a circle 20 kilometres wide around an area where sonar equipment picked up a signal on April 8th consistent with a plane's black boxes. The batteries powering those signals are now dead.

Both Australia and Malaysia are under growing pressure to show what lengths they are prepared to go to in order to give closure to the grieving families of those on board.

In a sign of the families' growing desperation for answers, a group purporting to be relatives of the missing flight's passengers wrote a letter to Malaysian defence minister Hishammuddin Hussein, urging the government to investigate old media reports that the plane landed in Kandahar, Afghanistan.

"It is high time that the government should start thinking out of the box by exploring and re-examining all leads, new and old," said the letter, published on Facebook on Wednesday.