Officials say a gas leak has led about 4,000 people to evacuate an industrial area of Columbus, Ohio.
Fire Battalion Chief David Whiting says firefighters were called at about 8 a.m. to Heartland Petroleum, which recycles oil. He says emergency medical crews treated three people and took one to a hospital.
Officials have identified the gas as both hydrogen and hydrogen sulfide. Whiting didn't immediately respond to a request for clarification.
He says tests now show the air is safe but people are not being allowed back yet.
Battalion Chief Doug Smith says a tank at the plant ruptured and crews are working to shut it down. He says the Environmental Protection Agency has been notified.