The United States Army Corps of Engineers has spent US$4m this year on the cleanup of three areas in the Northern Marianas contaminated by the US during and after the Second World War.
The CNMI's US Congress delegate Gregorio Kilili Sablan says work on three of the former defence sites on Saipan has been completed.
Another nine sites remain on the island.
In all, the Army Corps of Engineers has spentUS$ 9.5m over the last 10 years to clean up hazardous waste left behind by the US military in the CNMI.
Saipan was the site of heavy fighting between US and Japanese forces during the war.
Live ordnance and chemicals from the war are still being discovered on the island.