FORT MCMURRAY, Alberta, Can. -- Days after residents escaped a roaring wildfire in the Canadian city of Fort McMurray, the blaze shows no signs of abating.
The fire is marching on, forcing thousands of evacuees to pack up again and move farther south to outrun the flames.
Alberta officials have declared a state of emergency as they scramble to relocate thousands of evacuees who fled north to seek refuge.
"Our focus right now is on getting those people south as quickly as possible," Alberta Premier Rachel Notley said.
Here's what we know about the fire:
How did wildfire start?
The exact cause is unclear.
Authorities said it could have been sparked by a human, such as with a discarded cigarette or an out-of-control campfire, or by nature such as lightning.
Fort McMurray resident Cameron Spring said wildfires caused by the above elements are common in the area.
This particular fire started Sunday, raging out of control and torching hundreds of acres by early Friday.
And the weather is not helping. Authorities said high winds, high temperatures and dry conditions created "explosive conditions" for fire growth, making it difficult for firefighters to keep up.
How big?
The fire has torched at least 850 square kilometers (328 square miles) -- and growing. In addition to its size, the numbers it's left behind are just as staggering.
The mammoth inferno has destroyed at least 1,600 structures and forced nearly 90,000 people to evacuate.
As it rages, officials have been forced to relocate thousands of evacuees for a second time.
But there's one number that residents and officials are happy about: no fatalities.
"Take comfort tonight knowing that your friends and family are safe," local officials tweeted.
A blaze of that size is larger than Singapore, and bigger than Chicago and Boston combined, according to CNN meteorologist Dave Hennen.
Will it get better?
Depends on the fickle weather.
Temperatures are going up and down, but fierce wind gusts could fan the flames.
While soaring to 32.6 Celsius (90.6 degrees Fahrenheit) on Tuesday, temperatures dropped toward the end of the week, which might provide some relief to firefighters.
The temperature will be 18 C (67 F) on Friday, said CNN meteorologist Michael Guy. But whether the firefighters will catch a break depends on how strong the winds are.
Despite a dip in temperatures, fierce winds gusting in different directions pose a challenge.
"If it's constantly changing direction in different ways, it's hard to control a fire," CNN meteorologist Judson Jones said.
Is it the only fire burning in the province?
No.
There are 49 wildfires in Alberta, with seven considered out of control, officials say.
More than 1,110 firefighters, 145 helicopters and 22 air tankers are battling the blazes.
Is there any threat to Alberta's oil reserves?
Alberta has the third-largest proven oil reserves in the world, behind Saudi Arabia and Venezuela. So far, one of the largest oil companies in the region, Suncor, says none of its facilities have been damaged.
How can I help?
Several organizations are working to help evacuees.
The Edmonton Food Bank is accepting food and money donations that people can drop off at grocery stores and fire stations throughout Alberta.
To donate diapers, baby wipes, pillows and other items, reach out to the Edmonton Emergency Relief Services. The organization is also accepting monetary support for those not in Edmonton.
Others include the Canadian Red Cross, which is seeking monetary donations to provide shelter, clothing and food for evacuees.
