Crews work to contain oil spill on Charles River in Waltham

An oil spill in the Charles River in Waltham detected late Wednesday afternoon drew a large emergency response, including a hazmat team and state environmental investigators, authorities said.

Waltham police and firefighters responded shortly after 4:30 p.m. to a report of a strong odor of diesel coming from the area of 130 River St. behind Shaw’s supermarket. A large sheen of oil was visible on the surface. A hazmat situation quickly declared, officials said.

State Police and first responders from the Massachusetts Department of Environmental Protection were also on the scene.

Containment booms, which are used to absorb oil, were put on the surface to prevent the oil from traveling downstream, according to Ed Coletta, a spokesman for the DEP.

It is unclear how much oil spilled into the river. The source of the spill also was not immediately clear.

Coletta said investigators found a large oil accumulation upstream near 172 River St. More oil was found inside a storm water pipe system nearby and along several manhole covers, he said.

Samples taken near the manholes will be tested to see if they “match the oil in the river,” Coletta said. “We think they do.”

A private cleanup crew, National Response Corp., was called Wednesday night to help clean up the spill. They are expected to remain on the scene through Thursday, according to Coletta.

“We don’t know how much has spilled,” said Coletta. “Oil like this, it basically collects at the surface of the water.”