Forty shells left by Japanese troops during World War II have been found at a construction site in the city of Qiqihar in Northeast China's Heilongjiang province, local police said Saturday.

The shells were discovered last Sunday morning, when an excavator was being used at a construction site in the city's Jianhua district, according to the municipal public security bureau.

The fuze and bodies of the rusted shells were still intact and posed a safety risk. Police have moved the shells and stored them safely in a special warehouse, according to the bureau.

Two Japanese chemical weapon units were once stationed in Qiqihar when the city was occupied by the invading Japanese troops in the 1930-40s.

After the Japanese were defeated, large amounts of bombs, shells and mines were left behind. Undiscovered explosives still pose a threat to local residents.