A grass fire burning on the Altamont near Interstate 580 on Sunday afternoon snarled traffic for hours as first responders closed the freeway in both directions.
Cal Fire received the first reports just after 5 p.m. of the fire burning along I-580 near the Grant Line Road exit.
The 20-acre blaze grew quickly in the afternoon wind and jumped to both sides of the freeway.
California Highway Patrol officers closed westbound I-580 at the Grant Line Road and Mountain House Parkway exits and eastbound I-580 at North Flynn Road.
Traffic backed up along Mountain House Parkway and Patterson Pass Road as drivers were diverted off the freeway.
Altamont Pass and Grant Line roads were also closed over the Altamont as Cal Fire air tankers and ground crews fought the fire, which had consumed 500 acres by early evening.
Drivers who were stranded in the middle of the interstate road closure were escorted through the smoke by CHP officers.
The westbound lanes of I-580 were reopened around 9:30 p.m. Eastbound lanes were opened at midnight.
Drivers searched for routes around the fire as traffic stacked up bumper to bumper on back roads including Patterson Pass, Grant Line and Midway.
CHP dispatch logs recorded reports of several new fires during the night, all small, in the area of I-580 and North Flynn Road.
On Monday morning, Cal Fire declared the fire 100 percent contained with 640 acres burned. No cause was listed for the fire, which the agency referred to as the Grant Fire.