Michael Smith could see the smoke from his home in Dartmouth. (submitted by Michael Smith)Police in Nova Scotia ordered the evacuation of more than 400 homes Friday as a major forest fire spread near Dartmouth.

RCMP Cpl. Joe Taplin said the fire, fanned by high winds, had consumed an area almost two kilometres wide and about seven kilometres long by early Friday evening around Porters Lake.

Water bombers from New Brunswick arrived on Friday evening to help fight the fire, while another plane from Newfoundland is expected by Saturday morning.

"It's very windy down there and what's happening is the fire is spreading very quickly," said John Ross, a specialist in fire science at the Shubenacadie fire centre.

The air over parts of Halifax was thick with smoke, prompting authorities to warn residents to avoid strenuous exercise, stay indoors and keep doors and windows closed, the CBC's Tom Murphy reported.

The mandatory evacuation notice, issued late Friday afternoon, is for anyone living in the area from Mineville Road to West Porters Lake Road and east of Highway 107, including Candy Mountain Road.

Evacuees were being taken to the Porters Lake Community Centre. People living along O'Connell Drive were asked to leave earlier in the afternoon.

Plumes of smoke in the area, due to high winds before the fire jumped to the other side of a major road, forced a shutdown of Highway 107 between exits 17 and 19. Police said the road would remain closed overnight.

"All the smoke was coming across on the road and then, Boom, it looked like an explosion and the flames just blew across the road," witness Billy Hayden told CBC News.

Power outage affects 8,100 homes

The blaze damaged a transmission line, knocking out power to about 8,100 homes. Nova Scotia Power turned off electricity to other areas as crews battled the flames.

There are six other fires in the province, including one near Peggy's Cove, where a smaller number of residents were also being asked to leave their homes.

Fire officials said the fire index in Nova Scotia is either high or extremely high. Winds are expected to die down later Friday night.

Earlier in the day, crews from three fire stations in the Halifax Regional Municipality were sent to a heavily wooded area off Lake Loon Road in the Cherry Brook area.

The fires were burning in two large areas, including one near the Lake Major water treatment plant. No homes were threatened.

Crews were able to bring the fires under control, but because of the high winds, they called in a Department of Natural Resources helicopter to keep an eye on the situation from above.

With files from the Canadian Press