Avalon, Pa – Confusion over a natural gas valve apparently caused a house explosion that injured three people, including two hospitalized for burns, officials said.

Two men accidentally turned on the home’s gas line valve while trying to repair a leaky shower knob Tuesday, Avalon building inspector Chuck Kovacs said.

“As far as we know, a cigarette likely ignited the gas, (or) possibly incense,” Kovacs said.

Deputy Allegheny County Fire Marshal Don Brucker said the basement valves in older homes can lead to confusion.

“A lot of gas valves on older homes look like water valves,” Brucker said.

Two victims, identified only as Adam Krepps and Eric Franklin, are in Mercy Hospital in Pittsburgh in serious condition. A 19-year-old woman also in the home was treated and released.

The explosion caused a fire, and the rental home collapsed after the fire. No other injuries were reported.