MH370 Grieving and frustrated relatives of passengers still missing more than two years after their Malaysia Airlines flight vanished are scouring the east African coast for possible evidence that might help unlock the mystery of their fate.

Flight MH370, carrying 239 passengers and crew, vanished on its way from Kuala Lumpur to Beijing on March 8, 2014, sparking a search in the southern Indian Ocean that passed its 1,000th day last Saturday.

Relatives of the missing passengers are deeply unhappy and angry over the lack of progress made by official investigations.

A group of them - Malaysian, Chinese and French nationals - arrived in Madagascar last weekend in the hope of finding debris themselves and of raising awareness of the missing plane among local people and organisations.

Yesterday Jiang Hui, a Chinese man whose mother was on board the plane, discovered a small white piece of board in the sand on Madagascar's Riake Beach that he hoped could be a fragment from the cabin of the missing plane.

"I felt excited but at the same time it was saddening," he said.

"It is a small piece and won't really be able to show what happened to the plane but I hope so much that the authorities of Malaysia, China and Australia will try to find more."

Grace Nathan, a spokesperson for Members of Voice 370, an MH370 next-of-kin support group, wrote on Facebook of Jiang's find: "Such an emotional moment for all of us: sadness, hurt, confusion, excitement, hope."

Some family members have accused Malaysian-led investigators of focusing too much on the deep-sea search for wreckage off the coast of Australia, and have appealed to residents on the east African coast to search for plane debris and hand in anything they find to the authorities.

So far, three pieces of debris found on the beaches of Mauritius, Tanzania and the French island of Reunion have been confirmed to be from MH370. Investigators are examining several other pieces found in Mozambique and South Africa.

"It was a very emotional moment," Blaine Gibson, a self-funded American investigator accompanying the families in Madagascar, said of Jiang's finding.

"He found it at the small rocky cove at the north end of Riake Beach, the same place where I found the monitor case, debris and personal effects in June."

The search is expected to be suspended by the end of the year, when an Australian-led team completes its scouring of a 120,000-sq-km target area.

- Reuters