Pennsylvania ? A fire that may have been caused by an electrical cord connected to Christmas decorations swept through four downtown row houses Friday, killing five people and injuring several others, officials said.

The holiday decorations had been plugged into a power strip joined to an extension cord, Fire Capt. Robert Scheirer said.

The cause of the early morning fire was preliminarily ruled accidental. Investigators were trying to determine if the wiring failed, a specific ornament shorted out or if something else was involved, Scheirer said.

The row home where the fire started had no working smoke alarms. Three men and two women died inside, Scheirer said.

Firefighters were able to get the fire under control by 7 a.m., about half an hour after it started. They also rescued two adults and six children from a row house next door.

The injured were treated for smoke inhalation and released.

The other row homes that burned were either vacant or the people inside escaped on their own, Scheirer said. Four other houses on the street were damaged by smoke.