Both directions of Vasco Road between Livermore and Brentwood were closed Friday afternoon following multiple crashes and heavy fog, the California Highway Patrol said.

The Contra Costa County Fire Protection District said a fire captain was struck by a vehicle while tending to one of the crash scenes and suffered "a lower extremity injury," a spokesperson said. The fire captain's condition was not immediately known.

There was no word on other possible injuries, and drivers were urged to avoid the area and slow down in the fog. 

The CHP alerted about the road closure at 2:45 p.m., and the roadway was reopened by 4 p.m. 

The East Bay valleys have been experiencing heavy, persistent tule fog over the last two weeks and likely continuing into this weekend.  The latest dense fog advisory expired Friday morning, but may need to be issued early Saturday morning again for inland valleys and possibly the coast, the National Weather Service said.

During the closure, motorists in the Livermore area heading to the Brentwood/Antioch area were directed to take Interstate Highway 580 west to I-680 north to Highway 4 east, or take I-580 west to Tracy and north on the Byron Highway. 

This is a breaking news update. More information to be added as available.