Canada oil-sands producers, including Suncor Energy, could resume production within a week after the threat subsides from wildfires that cut as much as 40 percent of the region's output.

A quick restart depends on whether companies managed shutdowns properly and if power and pipeline infrastructure is unscathed, according to analysts at Wood Mackenzie Ltd. and IHS Energy. Suncor and Syncrude Canada Ltd., two of the biggest producers in the area that's been ravaged by wildfires near Fort McMurray, Alberta, both said they managed safe shutdowns. Only one oil-sands site, Cnooc Ltd.'s Nexen operations, has suffered minor damage.

"The best possible case, you're probably looking at somewhere within a week to get them restarted," said Harold York, vice president of integrated energy at Wood MacKenzie. Restarts will also depend on availability of workers after large-scale evacuations, which may be hindered given destruction of homes in the area, he said.

The bulk of the nation's large oil-sands projects shut some or all output in recent days, cutting supplies by about 1 million barrels a day, according to an IHS Energy estimate. Energy companies evacuated workers and shut upgraders, mines and wells as the inferno grew.

Suncor, Canada's largest energy producer, Syncrude, Husky Energy Inc., Imperial Oil Ltd. and Cnooc's Nexen are among operators that have taken output offline.

Suncor, which has closed about 700,000 barrels a day of capacity, said Sunday that it's beginning to implement a plan for resuming operations and will restart once it can do so safely. The company began shutting sites last week "in a controlled manner to facilitate a quick and reliable start-up," it said.

Syncrude, which can produce as much as 350,000 barrels a day, cut rates to a minimum when the fires began and then shut and evacuated all personnel from its Mildred Lake and Aurora oil-sands operations Saturday, according to a spokesman.

Houston-based ConocoPhillips has a team of people "working day and night" to figure out how and when the company can resume operations on its Surmont oil-sands operation, which was producing at 30,000 barrels a day before the blaze, said a spokesman.