TWIN CITIES, MN — The two-mile-long sheen spotted on the Mississippi River in the Twin Cities metro earlier this week was identified Friday as a lubricant used in the hydraulic system at the Coon Rapids Dam.

The lubricant is classified as “suitable for incidental food contact,” meaning it can come into contact with food and not cause harm, the Minnesota Pollution Control Agency (MPCA) told Patch. “Drinking water supplies remain safe.”

About 30 gallons of lubricant spilled into the river Tuesday when a valve malfunctioned during the adjustment of a dam gate, according to Three Rivers Park District, which operates the dam.

Crews deployed booms this week to divert the sheen away from city water intakes in Minneapolis and St. Paul.

The cities also temporarily closed their water treatment facilities intakes as a precaution, MPR News reported.

The Fridley Fire Department first reported a sheen on the river at about 1 p.m. Tuesday. The sheen was under the Highway 610 Bridge in Coon Rapids and traveled downstream, officials said.

At about 8:10 a.m. Wednesday morning, a smaller sheen was reported near the west shore of the river near West Coon Rapids Dam Regional Park, according to authorities.

“Additional drinking water samples have been taken and are being processed, but we do not expect them to indicate a concern for the safety of drinking water,” the MPCA said.