CRANSTON, R.I. (AP) — A pipe exploded at a chemical plant Friday, starting a raging fire that sent acrid smoke billowing through the building. Twelve people were injured, one critically.

The fire at the Technic manufacturing facility burned so intensely that pipes in the ventilation system melted, and firefighters used fans to clear smoke.

"We couldn't see from one end of the building to the other," Deputy Fire Chief Anthony Mastantuono said. As many as 200 people were evacuated from the neighborhood for about four hours.

Authorities said the pipe exploded after a worker banged on it with a hammer in an attempt to clear it. The worker was severely injured and in critical condition. The other 11 were treated for chemical exposure at Rhode Island Hospital and released, hospital spokeswoman Nancy Cawley said.