Environmental officials are trying to determine the cause of an oil slick in the Acushent River, near the sawmill property. An official with the Mass. DEP tells WBSM News the oil apparently entered the river from a combined sewer overflow pipe.

During their investigation, officials located a second spill at gas express on Tarkiln Hill Road and Belleville Avenue, but it's not likely connected to the spill in the river.

Officials are now looking at the possibility of the oil coming from a residence.

Two oil booms were placed around the storm drain to contain the spill.

Cleanup crews paused operations for the night, with the expectation of heavy rainfall. Efforts to remove the oil will continue Wednesday.