The California Highway Patrol received a call at 10:57 a.m. that a pickup truck went over the embankment on Highway 39 near the Morris Reservoir dam, and that the truck was catching fire.
Firefighters from the U.S. Forest Service and the Los Angeles County Fire Department were dispatched to the scene.
The blaze, dubbed the Reservoir Fire, has now spread to 1,500 acres. The driver involved in the accident was declared dead, according to the Los Angeles County Fire Department.
A second fire, called the Fish Fire, erupted nearby in the Duarte area about 90 minutes later. That fire has burned approximately 3,000 acres, with no containment.
The two fires appeared to be burning toward each other, spurring fears that they would merge. The Los Angeles County Fire Department said the two fires were separated by 1.5 miles.
Capt. Keith Mora of the Los Angeles County Fire Department said one firefighter was taken to the hospital with minor injuries after suffering from heat exhaustion.
Evacuations ordered in Azusa and Duarte
Azusa police ordered evacuations for Mountain Cove, Rainbow Canyon Ranch and El Encanto. An evacuation center was set up at Duarte Community Center, 1600 Huntington Dr., and at Memorial Park, 320 N. Orange Ave.
For the city of Duarte, an evacuation order was issued for homes north of Fish Canyon between Encanto Parkway and Greenbank Avenue, Brookridge Road and Opal Canyon Road.
Officials later announced extended mandatory evacuations for areas north of Markwood Street between Westvale Road and Greenbank Avenue, areas north of Deerlane Drive between Greenbank Avenue and Mountain Crest Road.
Residents in the Mount Olive Drive area just northwest of Conata Street, including residents in the Spinks Canyon Road, Rim Road, Goldenmeadow Drive, High Mesa Drive, and Tall Pink Drive areas were also mandated to evacuate the area.
Large animals can be taken to the Hansen Dam Equestrian Center at 11127 Orcas Ave. in Sylmar, and small pets can be taken to Wonder Dog Ranch at 220 Taylor St. in Monrovia.
Though there were no mandatory evacuations in effect for Monrovia, officials urged residents east of Myrtle Avenue and north of Greystone Avenue to prepare for possible evacuations if winds change direction or increase in intensity.
According to Los Angeles County Fire Chief Deputy David Richardson, 320 structures were evacuated near Azusa and 450 structures evacuated in the Duarte and Bradbury area.
Smoke advisory issued
Smoke from the forest fires was seen by residents across the Southland, including West Covina, Alhambra and Brea.
The South Coast Air Quality Management District issued a smoke advisory due to the fires. AQMD officials said air quality could reach unhealthy levels in areas impacted by smoke, including portions of the East San Gabriel Valley, the Pomona/Walnut Valley, the San Gabriel Mountains and metropolitan Riverside.
The public was urged to exercise caution and avoid unnecessary outdoor activities in any area directly impacted by smoke.
The Associated Press and City News Service contributed to this report.