Suspects Christopher Ortega, 20, and Santino Gnaulati, 21, were arrested Tuesday and set to be arraigned Thursday.
The Morris Fire, which burned about a quarter acre, was reported shortly before 3 a.m. near the dam off San Gabriel Canyon Road, north of Glendora. It was quickly contained, and no injuries were reported.
According to U.S. Forest Service officials, a bystander who reported the fire witnessed two men in a turnout near Morris Dam and took note of the vehicle description. With the help of Azusa police and Los Angeles County sheriff's officials, the vehicle was found and the two suspects were taken into custody.
Bail was set at $285,000 for Ortega and $75,000 for Gnaulati.