PHILADELPHIA (AP) _ A fire that may have been set swept through a rowhouse in north Philadelphia early today, killing three women and two children, police said.

Two men in the home were injured, and a firefighter hurt his back fighting the flames.

The blaze, which was brought under control in 20 minutes, started either by a firebomb or a flammable liquid poured through the front window, radio station KYW-AM reported, citing fire officials.

``This is suspected to be a homicide, we're treating it that way,'' fire spokesman Armand Gersbach told the station.

Homicide detective Aban Brooks would only confirm that police were examining the firebomb theory.

Witnesses reported hearing gunshots and a bang before the fire.

The identities of the victims, apparently all related, were unavailable.