The fire started on the Pittsburg side of northbound Kirker Pass around 4:20 p.m., said Tonya Hoover, fire marshal for the Moraga-Orinda Fire District.
Kirker Pass was shut down in both directions during the peak of evening commute. Eastbound traffic was redirected to Bailey Road and Highway 4 by Concord police and California Highway Patrol officers.
Two Contra Costa firefighters were injured around 6 p.m. when an engine rolled on a steep hill. They were flown to John Muir Medical Center in Walnut Creek with moderate injuries, Hoover said.
The fire burned about 20 acres and was contained around 6:15 p.m., Hoover said.
Jonathan Franks, a spokesman for Pacific Gas & Electric Co., said a truck knocked over a power pole on Kirker Pass shortly before the fire started.
"The truck knocked the pole over, took down some wire, and then we had a grass fire," Franks said.
Hoover could not confirm if the vehicle accident started the fire.
Approximately 4,292 customers in Clayton and Concord were without power for three to four hours. Franks said they hoped to have most customers' electricity back on by 8:30 p.m.
The southbound lanes of Kirker Pass were reopened around 6:30 p.m., but the northbound lanes remained closed at 8 p.m. with no estimated reopening time.
