Investigators in Ohio have ruled a fire that killed a 7-month-old and two adults was arson and the deaths are being classified as homicides.

Fire Battalion Chief David Whiting says the fire started near downtown Columbus early Friday on the porch of a house where there were no other possible sources of ignition.

Whiting says a fire dog picked up on evidence of arson and investigators suspect some kind of accelerant was used.

Whiting wouldn't discuss motives but says there were problems in the house, which is in a neighborhood where violence is common.