Officials have warned it could take three days to contain a wildfire in the Angeles National Forest in southern California.
Dubbed the Williams fire, it has scorched at least 3,600 acres and is said to have injured at least four people, including two firefighters.
The fire broke out near a campsite on Sunday afternoon in the San Gabriel Canyon area of the 655,000-acre Angeles National Forest.
It quickly grew to several hundred acres as flames chewed thick brush that was not touched by the destructive Station Fire in 2009.
The Angeles is fewer than 15 miles from Los Angeles at its southern end. It is one of the most heavily visited national forests with about 30 million annual visitors.
Earlier this week thousands of visitors were evacuated from Southern California due to the blaze.