P.E.I.'s deputy provincial fire marshal David Rossiter said the fire started on the outside patio area. (CBC)

The provincial fire marshal has wrapped up his investigation into a fire that destroyed a home early Saturday morning in Montrose, P.E.I.

A family of three had to climb through the living room window after fire blocked the main doorway to escape the blaze.

Police received a call at 12:45 a.m.

Provincial Fire Marshal Dave Rossiter said the fire started on the outside patio area where the electrical service entered the home.

He said the fire was caused by a fault within the incoming circuit.

Rossiter said there were working smoke alarms, but because the fire began outside, the alarm notification was delayed.