A letter from Edison to the Public Utilities Commission says U.S. Forest Service investigators have not shared details of the investigation, but they have retained a section of SCE's overhead conductor line and three tree branches from the area where the blaze first started.
"SCE is investigating the cause of the ignition and the 12:16 p.m. relay on its system, and evaluating whether vegetation in the area could have been a factor, including whether vegetation may have encroached within the minimum clearance distance or contacted the section of the overhead conductor retained by USFS,'' the letter stated.
Bobcat Fire: SCE utility equipment eyed as possible source of blaze in San Gabriel Mountains
The fire was reported near Cogswell Dam in the Angeles National Forest at 12:21 p.m. on Sept. 6. A camera at Mount Wilson captured smoke in the area as early as 12:10 p.m.
On Sept. 16, Edison removed a 23-foot-long line of the conductor for the U.S. Forest Service to use in their investigation.
After more than a month, the fire has burned nearly 116,000 acres and is 92% contained.
The blaze has destroyed 171 buildings, including 87 homes.
City News Service contributed to this report.