Highway authorities on Sunday reopened nearly all lanes of Interstate 5 freeway near Castaic, California, roughly 40 miles northwest of Los Angeles, after firefighters helped mitigate a wildfire that had spread across dry hillsides.

The Route Fire, aided by 10-15 mph winds, broke out at about 4 p.m. on Saturday and spread over half of a square mile, burning over 450 acres. 

“Firefighters made progress overnight with the help of water-dropping aircraft and an aggressive ground attack,” said Andrew Mitchell, a spokesperson from Angeles National Forest.

Two firefighters were injured and taken to a hospital for burns.

Thunderstorms had swept across the region on Thursday and Friday. Temperatures in the region Sunday reached 97 degrees.

An investigation is underway into the cause of the wildfire.

Castaic has a population of about 20,000. Thousands of drivers daily pass by the small city on Interstate 5.