Wildfires continued to blaze through the heart of Canada’s oil patch, expanding to cover 1,000 square kilometres in what is expected to be one of the costliest natural disasters in the country’s history.

The forest fires destroyed large parts of Canada’s oil sands capital, Fort McMurray, this week, forcing the evacuation of about 90,000 residents and shutdowns at plants in the world’s third-largest oil production hub.

“The fire continues to burn out of control,” Rachel Notley, Alberta’s premier, said on Friday. “The wildfire is still unpredictable and the evacuation needs to be co-ordinated and safe,” she added, promising a gift of $1,250 to each adult and $500 to dependants who were evacuated.

A convoy of about 1,500 vehicles began taking evacuees from Fort McMurray early Friday morning, leaving in groups of 50 vehicles guided by police and military helicopters.

A mass airlift of evacuees was expected to resume on Friday, a day after 8,000 people were flown out of the town, with the hope that 5,500 would be evacuated by the end of the day.

So far the blaze has destroyed about 1,600 buildings, although Ms Notley warned that final toll could be ‘much bigger’.

The fires reduced crude output from the oil sands, with companies including Royal Dutch Shell, Suncor Energy and Syncrude curtailing operations to evacuate workers or offer shelter for fleeing residents. As much as 1m barrels per day, or 40 per cent of oil sands production, was potentially at risk, according to Platts Analytics.

Oil futures briefly jumped on Thursday as the fires spread but ended the week lower amid plentiful global supplies.

Economists have cut their outlook for Canada’s economy since the fires erupted. Robert Kavcic, a senior economist at BMO Capital Markets, now expects no growth in the second quarter, having previously projected a 1.3 per cent annualised gain, with most of the reduction because of the wildfire.

The fires could cost insurers as much as C$9bn, according to Bank of Montreal Capital Markets. Analyst Tom MacKinnon said it was more likely that one-quarter to half of assets in the region would be damaged, leading to total insurance industry losses of C$2.6 billion to C$4.7 billion, or as much as four times the costliest Canadian natural disaster to date.

Canada’s federal government has promised to match individual donations to Red Cross Canada from May 3 through May 31. Some C$30m in donations have been received so far, the Canadian Press reported. “The city that contributed so much to Canada’s economy over the years needs our help. We’ll be there for Fort McMurray”, prime minister Justin Trudeau tweeted on Friday.

Syrian refugees in Calgary, a city south of Fort McMurray, donated money to those escaping from the fires after Rita Khanchet, a Syrian who fled her country five months ago, posted an appeal on Facebook, said a report by the Calgary Herald.

Additional reporting by Gregory Meyer