ROCKVILLE, Md. (AP) — Several oil tanks caught on fire late Thursday morning at a quarry in the Maryland suburbs of Washington, D.C., sending thick plumes of black smoke into the air that were visible for miles.

The fire was contained by early afternoon while three tanks continued to burn, Montgomery County Fire and Rescue spokesperson Pete Piringer said during a 2 p.m. news conference. Officials said no injuries were reported.

Piringer said two of the tanks contained liquid asphalt and the third contained used motor oil.

He said the cause was not yet known.

The nature of the fire means crews can’t use water to put it out, but Piringer said they have no shortage of the appropriate chemical agents.

Piringer said that since the fire was contained, officials were focused on monitoring the air quality in communities near the Rockville industrial site. He said there was no significant health risk but residents in those areas should limit time outside and close their windows when possible.

State environmental officials were on site and all workers had been evacuated from the immediate area of the fire, Piringer said.

Rockville is about 15 miles (24 kilometers) northwest of Washington. The fire was reported just before noon Thursday.