JACKSONVILLE, Fla. -- One man was critically injured in an early-morning fire at a home on McCowan Drive on the Westside.

Firefighters responding to a 5 a.m. call of a house on fire found a man had dragged himself onto the front yard. He was transported to Shands-Jacksonville Medical Center. His name was not released.

The fire was primarily confined to the front of the home.

As soon as the fire was out, investigators began looking for a cause of the fire.

"The actual investigation will primarily focus on space heaters ... although we cannot determine yet whether space heaters that have been found in the home were actually active," Jacksonville Fire-Rescue spokesman Tom Francis said.

Later in the day, the state Fire Marshal's Office told Channel 4 it had ruled out the space heaters and believed the cause was electrical in nature.