A house fire in the Ashby area of Sydney has been ruled suspicious in nature. (George Mortimer/CBC )

Cape Breton police are searching for a man they believe deliberately set a house on fire in Sydney on Saturday morning.

Firefighters were called to the home on Forrest Street just before 6 a.m.

Three people were in the house at the time of the fire. There were no reported injuries.

"The male was at the residence earlier, and at this time we believe it's a possibility the fire was set. As a result we were looking for the male subject that left the house," said Cape Breton Regional Police Staff Sgt. Reg Hutchings.

Fire Platoon Chief Paul Feguson said it was a difficult fire to battle.

"We did an interior attack with firefighting crews to contain the fire. There's been significant damage to the structure. The heat posed a problem. We had to rehab some firefighters during the course of the operation," he said.

Police posted security at the site on Sunday afternoon. Officials from the fire marshal’s office will join the regional police's arson section in the investigation on Monday.

Ferguson said the Canadian Red Cross is sheltering at least one person who lived in the home.