(CBS) – A hazmat response team swarmed a hotel in northwest suburban Rosemont Thursday night amid concern there could be a possible meth lab operation there.

The incident began around 4:30 p.m. at the Hampton Inn, 9480 W. Higgins Road, when an employee reported a fire in a guest room. Responding police discovered “suspicious materials” inside the room, prompting the evacuation of the 158-room hotel, the Rosemont Public Safety Department said in a news release.

Sources tells CBS 2 materials found at the scene could be that of a meth lab but will need to be tested.

Rosemont detectives have two suspects in custody and are treating this incident as a criminal matter, police said.

One guest was transported to an area hospital.

The displaced guests were moved to another hotel, officials said.