A mass grave with more than 100 sets of remains believed to be those of communist soldiers killed during the Vietnam War has been uncovered, and some had nails embedded in their skulls, an official said Monday.

Construction workers found the first five sets of remains two weeks ago while digging a drainage system for a sports complex in Central Highland province of Gia Lai, about 310 miles north of Ho Chi Minh City, said the official from the provincial military command. He identified himself only as Son.

An army excavation team later uncovered 103 more sets of remains from the grave, Son said.

CountryWatch: Vietnam

He said that many personal effects such as mirrors, combs, watches and pens also were found, and that many of the skulls were pierced. Handcuffs also were found, he said.

Authorities suspected that the communist soldiers may have been arrested during the Tet Offensive in 1968, Son said.

The remains, all unidentified, were buried at a military cemetery Saturday, Son said.

In 1997, authorities uncovered 60 sets of remains in the same area, the official said.