Fuel shortages and heavy traffic has delayed the evacuation of all 80,000 residents from a Canadian city where a wildfire rages out of control, destroying more than 600 homes.
Firefighters in Fort McMurray, in the province of Alberta, faced another tough day on Wednesday as hot, dry weather made it difficult to bring the fire under control.
While major oil sands facilities were not in the fire's path, the blaze disrupted some operations.
Royal Dutch Shell said one of its oil sands mines was closed and another was in the process of being shut down.
Suncor Energy, whose oil sands operations are closest to the city, said it was reducing crude production.
The regional government on Tuesday ordered the city's evacuation, and some 44,000 had since fled, local officials said, but getting out remained difficult.
A highway closure forced most evacuees to drive north, away from major cities.
By Wednesday morning, the highway had reopened, but fuel had run out, stranding evacuees.
Alberta authorities are escorting a fuel tanker north to help stranded drivers.
Images from the neighbourhood of Beacon Hill in the city's southeast showed rows of charred foundations of homes, their upper stories burned to the ground, and blankets of white ash within.
Officials said 80 percent of houses in the neighbourhood, nearly 600 in total, were destroyed.
The regional government said two other neighbourhoods, Abasand and Waterways, had sustained "serious loss".
The fire broke out southwest of the city on Sunday, then shifted with the wind to enter the city on Tuesday.
A forecast of potential fire intensity showed much of the area at the highest possible level.
No injuries or deaths were reported.
Officials said their priority was protecting people and preserving key infrastructure, including the city's only bridge over the Athabasca River and Highway 63, the only route in and out of town.