(CNN) -- A wildfire in San Bernadino County, California, scorched some 300 acres and burned at least one home in a matter of hours Monday, according to the U.S. Forest Service.
The fire, called the Ken fire for a local freeway exit, was about 20% contained seven hours after it was first reported, with more than 500 firefighters, 18 fire engines and 11 aircraft working the blaze, according to Forest Service spokeswoman Angelica Mendoza.
Northbound traffic on Interstate 15 through the fire area was backed up for several miles due to lane closures, with one northbound lane remaining closed into the evening, Mendoza said. Southbound lanes remained open.
No cause of the fire had been determined, Mendoza said. One firefighter was injured, she said, and one ranch in the area was evacuated. The fire was first reported about 1 p.m. Monday in a mostly rural, sparsely populated area of the sprawling county in southeast California.
A separate fire also in San Bernadino County consumed about three acres before it was contained, according to the county fire department.