SUNAPEE โ€” Firefighters responded to a report of an unknown substance in Sunapee Harbor off Main Street Sunday evening.

Firefighters are awaiting results from the New Hampshire Department of Environmental Services, DES, to confirm if the substance is fuel, but confirmed that there was a “large sheen covering a portion of the harbor” near 71 Main Street just before 5:30 p.m. Sunday, according to a social media post from the department.

Sunapee Fire Department, the DES, Midwestern New Hampshire Hazardous Materials Team and Sunapee Police Department worked to contain the spill Sunday.

Crews deployed containment booms and took a sample of the substance for testing to determine the “source and composition of the spill.”

The containment booms block some docks in the harbor. Officials ask that boaters do not move, disturb, or try to go around the containment booms.

“We understand this is an inconvenience, especially during the busy summer boating season, but the cooperation of the community is critical to ensuring the spill is successfully contained and removed,” the post said.

Officials also responded to an oil spill in Georges Mill Harbor in Sunapee May 6 caused by a broken hydraulic line on a tow truck. The spill was completely cleaned up by May 16, according to a post from the Sunapee Fire Department.

Last week, the Woodstock Fire Department responded to a fuel spill in the Ottauquechee River after a truck turned over on the bank.

Clare Shanahan can be reached at cshanahan@vnews.com or 603-727-3216.