Lebanon, OH – Residents say they heard an explosion like a bomb going off before a fire that ripped through an Ohio townhome complex and injured seven people.

Local fire officials in Lebanon said that Tuesday night’s fire resulted when a woman lit a cigarette in a unit where natural gas was leaking. The Ohio Fire Marshal’s office said Wednesday it was not ready to confirm a cause.

Three children and two adults were treated at a hospital and then released. A woman and a 13-year-old girl were taken to a hospital in Dayton, 24 miles away in southwest Ohio. Fire officials expected both to recover.

Ten units in a two-story building were either destroyed or heavily damaged. The American Red Cross is helping with shelter for displaced residents.