A Malaysia Airlines towelette was found on a Western Australian beach four months after MH370 vanished, investigators revealed Tuesday, but they said it was impossible to know if it came from the missing plane.

Flight MH370 disappeared on March 8, 2014 with 239 people on board and no sign of the aircraft has ever been found. It is thought to have gone down in the Indian Ocean off Australia's west coast.

It emerged that a towelette -- a wet wipe usually served on board with drinks or meals -- with the Malaysia Airlines logo was discovered on a beach at Thirsty Point, some 200 kilometres (124 miles) north of Perth.

The Australian Transport Safety Bureau (ATSB), which is leading the underwater search for the plane, has previously looked at items washed up on beaches in Australia's west but none have ever shed light on what happened -- and it said the towelette was no different.

"A 6cm x 8cm moist towelette in wrapping branded with the Malaysia Airlines logo was found at Thirsty Point on 2 July 2014. It was handed in to the Western Australian police," the bureau said in a statement after the discovery was reported by Australian media.

"It is unlikely, however, that such a common item with no unique identifier could be conclusively linked with MH370."

One year on, mystery continues to surround the fate of the Boeing 777-200 aircraft that disappeared from air traffic control radar after taking off from Kuala Lumpur on a flight to Beijing.

Analysis of satellite data later revealed it flew for more than six hours after contact was lost, and suggested it crashed into the southern Indian Ocean after running out of fuel.

Malaysia's handling of the disaster has been criticised from the start and an interim investigation report released Sunday uncovered a dud beacon battery and more potential missed opportunities to track the plane.

However, the airline said the battery on the separate cockpit voice recorder -- good for 30 days once activated -- was up-to-date and would have transmitted a signal once it hit water.

- 'Families deserve answers' -

Sunday's report said investigators had probed a range of issues including the personal, psychological and financial profiles of the jet's captain Zaharie Ahmad Shah and his co-pilot Fariq Abdul Hamid, as well as the backgrounds of the 10 cabin crew.

But although some suspicion had fallen on the cockpit crew, the report mentioned no evidence implicating either of them.

It also said that according to available data and maintenance records, nothing alarming was detected in the plane's major mechanical systems.

Australian officials have expressed cautious optimism that the plane would eventually be found, and Deputy Prime Minister Warren Truss said Canberra, along with Malaysia and China, remained committed to the search.

So far more than 26,000 square kilometres -- over 40 percent -- of the priority zone of the seabed where the plane likely went down has been searched using specialist equipment.

"The families deserve answers and we are doing all we can to get them," Truss said.

Searchers hope to have completed the designated underwater search area by May.