The Calabasas brush fire that scorched over 500 acres and forced at least 5,000 residents to evacuate their homes was reported to be 75 percent contained as of late Sunday evening.

That hardly spelled the end of danger for residents, as the entire community remained under mandatory evacuation and authorities worried sweeping winds could easily cause all the flames to reignite.

At Least 400 Firefighters on the job

Indeed, the part of the fire that continued to burn late Sunday is reported to be in rugged terrain that's hard to access and is often home to sweeping winds. Approximately 400 firefighters are still on duty battling the blaze.

"We can drop all the water all day," said Deputy Fire Chief John Tripp. "It's got to be boots on the ground to make sure that fire's out."

The blaze is believed to have been sparked on Saturday after a truck struck a utility pole. Some residents were allowed to return to their homes as early as Saturday night, but were warned they could be without power.

The entire community of Topanga also remained under mandatory evacuation orders as high temperatures and dry conditions caused "hundreds" of smaller fires to merge into one."

Thus far, three firefighters have been reported injured, with one of them described as suffering a cardiac event and the other two knee injuries.

Calabasas is home to roughly 24,000 residents, including several affluent gated communities were such celebrities as the Kardashian family are known to reside.

Driver Speeding?

Witnesses have told authorities the truck involved was traveling at a high rate of speed when it struck the pole, causing it to fall atop a transformer.

The blaze has been dubbed the "Old Fire" due to its proximity to Old Topanga Canyon Road. It came right up to the edges of Calabasas High School and Viewpoint School.

For much of the weekend, temperatures hovered in the mid-90s, making the challenge of battling the blaze even more intense.