The cause for Wednesday's Donner Summit fire: workers cutting down trees that fell on a power line.
Sierra Pacific Power Company spokesman Karl Walquist says the company, which he declined to identify, had been hired to remove hazardous trees from the vicinity of power lines.
Walquist says Sierra Pacific has met with the company to ensure such accidents won't occur again.
The blaze at the Truckee exit broke out shortly before two and the interstate was closed a short time later. It reopened about 5:30 after westbound traffic had backed up for miles.
Hundreds of homes were in the area of the blaze, but no evacuations were ordered and engines were positioned to protect homes and buildings.
There were no injuries.