A report from the Northern Marianas says more than 2 million kilos of unexploded World War II ordnance is being held at a secure storage area in Marpi on the island of Saipan
The Saipan Tribune quotes, Jim Callier, the special assistant to the director of the Division of Environmental Quality, as saying most of the explosives were stored in the Marpi area in preparation for the invasion of Japan in 1945.
He said thousands of kilos were also left behind by the Japanese army when they were driven out of the Marianas.
Mr Callier said local residents digging for construction of houses and other projects in the area should have the land surveyed first using a magnetic metal detector.
If any metal objects were found authorities should be called in.
The EMO, together with the Department of Public Safety and the U.S. military, have been regularly detonating unexploded shells in 450 kilo lots.
The last detonation was held two months ago.