Firefighters managed to contain the flames largely to the attic of the manor known as Earnscliffe, but there was much damage to the roof and interior.

British High Commissioner Andrew Pocock and his wife Julie, who live in the home, and his house guests, were forced to flee into the night after the fire broke out at 140 Sussex Dr. at 7:35 p.m. Pocock said he'd smelled smoke in the kitchen shortly before sounding the alarm.

"We weren't frightened. We were alarmed and concerned in a house full of smoke," Pocock said outside the main gates of the estate.

Asked what he was doing at the time: "Well, what one does at 7:30 p.m. -- making dinner," he said in a very proper British accent.

"The house was suddenly full of smoke, but the brigade arrived very quickly, and as I say, everyone's safe and the house itself seems to be, broadly speaking, intact, although there will be smoke and water damage."

Pocock tried to find the source of the fire, he said, and determined it was somewhere on the upper floor.

"(We) did the sensible thing -- got out of the house and left it to the professionals," he said.

Foreign Affairs Minister John Baird, who was passing the scene after leaving nearby work, offered the Pococks the use of 7 Rideau Gate -- the official guest house -- should they need it.

As the party safely left the building, the kitchen and much of the mansion filled with smoke.

Firefighters found flames in the attic near the chimney, which quickly spread into the walls.

"We brought in some extra crews, just mostly for salvage operations," fire spokesman Marc Messier said, adding the crews were trying to save valuables.

He said much of the damage was contained to the attic, but crews used chainsaws to cut through walls and the ceiling to douse any flames that might have spread farther into the old building.

"That's the big problem. There's a lot of void because of the way it was built. The type of wood is dry, and the insulation poses a problem as well," Messier said.

Firefighters were forced to fight the blaze from inside because the steel roof prevented an approach from above.

By 9:15 p.m., the fire was under control, but firefighters were still dousing hot spots.

"We have no idea what caused it. It's an old house," Pocock said. "The fire assessment people will come tomorrow and tell us."

The home belonged to Sir John A. Macdonald from 1883 until his death in the mansion in 1891 and is a one of the country's national historic sites.

The cause of the blaze is under investigation.