Hanoi, Dec 3 (DPA) Authorities have discovered a mass grave containing the remains of at least 25 Vietnamese soldiers killed in combat 41 years ago, an official said Thursday.

“They belonged to a commando company killed in 1968 while trying to liberate Quang Ngai prison,” said Lieutenant Colonel Nguyen Trong Luyen, commander of the military forces in Quang Ngai City. “We have not determined how many remains are there, but I think there will be more.”

Quang Ngai prison was used by the former government of South Vietnam to detain prisoners of war from the north.

The commandos tried to free their comrades as part of the Tet Offensive in early 1968. The attack failed, and almost all the commandos were killed, Luyen said.

On Tuesday, workers from a company constructing a drainage system near the former Quang Ngai General Hospital found bones and other items, including caps and uniforms, buried two metres underground.

Quang Ngai authorities began excavating the area Wednesday.

Le My Lien, chairman of the Quang Ngai Province People’s Committee, said the excavation had been scheduled to take one day, but that more remains had been unearthed.

The Tet offensive was launched by North Vietnamese forces during the lunar New Year, or Tet, of 1968. The offensive failed, leaving an estimated 44,000 guerrillas dead and 60,000 injured.

An estimated three million Vietnamese were killed in the Vietnam War, along with over 58,000 US soldiers. The war ended with the victory by northern forces in 1975.