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Two-thirds of the passengers were Chinese, while the others included Malaysians, Indonesians and Australians, as well as Indian, American, Dutch and French nationals.

Despite multiple searches, including the largest in aviation history, neither the aircraft, passengers nor black boxes have ever been found. 

The latest search, which began in December, scoured an area of around 15,000 square kilometres but efforts "have not yielded any findings that confirm the location of the aircraft wreckage", Malaysia's transport ministry said in a statement.

Exploration firm Ocean Infinity, based in Britain and the United States, led the search which concluded on January 23.

Families of the Chinese passengers published an open letter on Sunday -- the 12th anniversary of the flight's disappearance -- criticising the lack of information they received during the latest search.

"We understand the difficulties of the search," the relatives said in an joint open letter to Malaysian Prime Minister Anwar Ibrahim, in which they thanked him for the initiative.

"However, since 15 January this year, families have received no further search briefings whatsoever."

"Over the past two months, we have repeatedly contacted Malaysia's Ministry of Transport through both Malaysia Airlines and the Chinese government, yet have received no response," they said.

In an attempt to locate the aircraft, Ocean Infinity deployed autonomous underwater drones capable of diving to depths of up to 6,000 metres (20,000 feet).

The company conducted previous unsuccessful searches in 2018, as did Australia for three years until January 2017.

In their letter, the Chinese families added that "for 12 years, we have received virtually no genuine psychological support". 

"We ask for little: only to be seen, to be heard, and to be treated as individuals with emotions and dignity."

The families are expected to be received by China's foreign ministry on Monday, as they are every year, before visiting the Malaysian embassy in Beijing to deliver the letter for Anwar.

ehl/dhw/mtp