Alberta officials issued an expanded order Tuesday. Nearly 53,000 people had moved to safer ground, authorities said.
Extremely high temperatures and low humidity fueled the blaze, leaving firefighters battling "explosive" conditions.
"All our efforts to control and contain the fire were challenged by this extreme fire behavior," said Bernie Schmitte, the forestry manager. "Efforts were also hampered by smoke conditions. Basically fire behavior was beyond all control efforts."
No injuries or casualties have been reported.
Homes, businesses engulfed
Nine air tankers and 100 firefighters have been battling the blaze, which began Sunday. The fire was estimated to be 7,400 acres as of Tuesday, according CBC News.
The blaze has engulfed homes and businesses but the exact number of burned structures is unknown, according to the Alberta Emergency Management Agency.
With a population of more than 60,000 in Fort McMurray, the evacuation is the largest in Alberta's history, according to CBC News.
Authorities said the number of people evacuated so far is an estimate and the full picture will emerge when the blaze is contained.
The only hospital in the city, Northern Lights Regional Health Centre, evacuated all 105 patients, the Alberta Government said.
Prime Minster Justin Trudeau tweeted his support.
"My thoughts are with people affected by the fire in Fort McMurray tonight," he posted. "We stand ready to help."
Residents used social media to share their images of the massive wildfire enclosing their town.
"I am out. I am safe," tweeted one resident. "I've never been more scared in my life. Praying for my home right now."
William Stephen Jeffery captured video of the black smoke and orange flames approaching a building in Fort McMurray.