By Nga Pham
BBC News, Hanoi
Workers at the site have been finding human remains every day
Developers say they have discovered the remains of at least 50 anti-French resistance fighters and war victims at a site in central Hanoi.
Workmen found bones and skull fragments while clearing the site of a market.
They also found handcuffs and leg irons, which suggested that some of the dead were prisoners.
The grave dates from 1946-1947, when fighting between Vietnamese resistance and French troops reoccupying the country after World War II broke out.
The market on top of it was built in the early 1980s and was named 19 December Market, after the day in 1946 that the anti-French movement began.
But it quickly became known as Cho Am Phu, meaning Hell Market, to commemorate the dead buried underneath.
Also found at the site were old coins and buttons with foreign insignia, indicating some foreigners, most probably French, were buried there too.
Although the authorities attempted to remove the remains in 1982, new finds prove that there are still a large number of bodies left behind.
Pham Van Toan, who was working at the site, said the digging began at the weekend. Workers had found human remains "everyday since", he said.
The remains will be reburied outside the Vietnamese capital
"It is impossible to tell how many they are, or who they belong to," he added.
Mr Toan and others were instructed to wrap the remains in red cloth and put them in small terracotta coffins. They will then be transferred to be reburied outside Hanoi.
Altars have been erected and incense sticks are being burned at the site; a prayer ceremony for the deceased is being planned.
Hanoi authorities have set a target of clearing all the remains before the Lunar New Year, which falls on 26 January.
The former market was to be developed into a multi-storey shopping complex, but the plan was scrapped last week after historians, architects and the public voiced their concerns.
Duong Trung Quoc, a well-known historian and MP, sent an open letter to Hanoi Chairman Nguyen The Thao asking city authorities to retain the "remembrance space that bears great historical significance".