According to an East Contra Costa County Fire Protection District report, four victims suffering from major injuries were transported to hospitals, including one sent by helicopter to John Muir Medical Center in Walnut Creek.
ECCFPD Chief Hugh Henderson said the incident began with a head-on collision followed by several rear-end crashes. A number of vehicles were reported to have left the roadway.
Lanes in both directions were closed for some time, but have since been reopened. The California Highway Patrol is investigating what caused the accident.