Fire crews battled a massive brush fire in Riverside County on Wednesday.

The Rock Fire was burning just east of Lake Perris and was first reported at 75 acres and burning at a dangerous rate of spread around 2:35 p.m., according to CAL FIRE/Riverside County Fire Department.

By 4 p.m., the flames were burning around 106 acres and by 5 p.m., the blaze had expanded to 150 acres and still growing. By 9:30 p.m., the fire had swelled to 500 acres with 75% containment.

Sky5 video showed flames and heavy smoke covering a brush area and hillside. A large burn scar can be seen on the hillside as well.

Firefighters and air tankers responded to the scene and are working to extinguish the flames. It’s unclear what ignited the fire.

“Firefighters will remain on-scene throughout the night and tomorrow, working on strengthening containment lines and continuing mop-up,” CAL FIRE said Wednesday night.

By Thursday night, the fire had expanded to 532 acres and was 100 percent contained, officials announced shortly before 7 p.m.