Police and firefighters evacuated 35 homes in the 6400 block of Ravena Drive Friday after investigators found potentially explosive chemicals inside house suspected of being a meth lab.

Lt. Mike Craft, of the Butler County Sheriff’s Office, said the county’s Regional Drug Task Force was executing a search warrant for a possible meth lab at the Ravena Drive home when “upon entering the residence, we discovered a lot of precursors for explosives and things that may be dangerous.”

Units from the Fairfield Twp. police and fire departments, the West Chester Twp. fire department, the Butler County Sheriff’s Office and the Butler County Emergency Management agency were clustered for several hours around the street where the unspecified chemicals, powder and devices were found. Officials from the FBI and the DEA were also on the scene.

Fairfield Twp. police Chief Richard St. John said officers took a man and a woman into custody at the home, but he would not release their names. The female — who complained of chest pains at the scene but refused treatment — was arrested on existing warrants, he said. Charges have not yet been determined, but St. John said they could relate to drug activity.

According to Butler County property records, the home is owned by Stephen and Dolores Fishwick and is valued at $95,000.

Officers found both liquid and powder chemicals, along with other unknown substances, in the house, the garage and the basement, authorities said. Fairfield Twp. Fire Chief Tim Thomas said there were at least two open containers that posed a potential threat.

The neighborhood evacuation was called off shortly after 6 p.m.

St. John said the department had been receiving tips about the residence for the past couple of weeks, “but the investigation really got under way on a serious basis in the last couple of days.”

Tony Day, who lives next door to the home that was searched, said he had seen authorities at the house earlier this year. He said he did not know much about either the man or the woman.