OPAL, Alta. - Residents of a rural area north of Edmonton were told they'd have to leave their homes on Sunday as gusty winds caused a brush fire to spread.

Radio broadcasts were interrupted by the province's emergency broadcast system just after 4:30 p.m., warning residents of a rural area near Opal, Alta., that they'd have to leave the area immediately.

Evacuees were told to gather at a community hall at Half Moon Lake near Vimy, Alta., about 60 kilometres north of Edmonton.

Brisk winds have created a worst-case scenario for over 200 firefighters battling the flames, said Brydon Ward, a wildfire information officer with Alberta Sustainable Resource Development.

Winds gusting up to 30 kilometres per hour caused flames to jump a wide strip of bare earth on the northwest corner of the blaze Sunday afternoon, he said. The fire was growing larger and for safety reasons, Ward said they had to pull fire crews out of the area.

"It's caused us to back off with some of our firefighters," he said in an interview from the fire command centre in Opal, Alta.

The only solution was to wait until the winds die down, Ward said.

Two rural properties within a couple of kilometres of the blaze considered to be at risk from the flames were being protected, he said. Bulldozers scraped a wide patch of bare earth around the properties in an effort to prevent flames from reaching the homes.

"We have put sprinkler systems on the roofs of the outbuildings and the homes. We've got water protection and fire trucks sitting there in the event that something does happen," Ward said.

Seven helicopters with large water buckets were dousing the flames earlier in the day, but heavy smoke grounded them. On Saturday, provincial officials estimated that the fire had charred roughly 22 square kilometres but the smoke was too thick on Sunday to allow them to map its latest size from the air.

Ward said there's not much firefighters can do except wait for the winds to die down.

Humidity was expected to be higher and the winds much calmer by Monday, Ward said.

" (Winds) about 15 kilometres per hour, we can work with that."

Peggy Hardinge, a public affairs spokeswoman with Westlock County, said she wasn't sure how many residents may be affected by the mandatory evacuation order.

The area around Half Moon Lake has some recreational properties, but there are likely permanent residents as well, she suggested.

A handful of county staff gathered at the area's community hall, prepared to register evacuees and offer them a place to stay the night and get a meal, if necessary, Hardinge said.