UPDATE 5-Wildfire in Alberta's energy heartland forces thousands to flee
* Fire shifts aggressively on Tuesday to breach city limits
* Authorities issue mandatory evacuation order for Fort McMurray
* Suncor says cutting output to allow employees to get to safety (Adds Suncor production impact, Shell and Nexen statements)
By Nia Williams
CALGARY, Alberta, May 3 (Reuters) - Alberta is racing to evacuate thousands of people as an uncontrolled wildfire burns near Fort McMurray, in the heart of Canada's oil sands region, forcing residents to flee north to safety on Tuesday.
Alberta appealed for help from other provinces and Ottawa to help fight the fire and airlift people from the city. Authorities issued a mandatory evacuation order for all of Fort McMurray, which affects the city's 80,000 residents.
The 2,650-hectare (6,540-acre) fire, which was discovered on May 1, shifted aggressively with the wind on Tuesday afternoon to breach city limits. The blaze closed off the main southern exit from the city, prompting residents to head north towards the oil sands camps.
"This is the biggest evacuation we have seen in the history of the province," Alberta Premier Rachel Notley said at a news conference, adding that there were no casualties in the fire.
"We need to find more camps, we have secured spaces for about 6,000 people, we know we need to find more and that work is underway," Notley said. Continued...