The crash happened at about 6:20 a.m. at the intersection of Balfour Road and the Highway 4 Bypass, Hansen said.
When police arrived, they saw a van lying on its side and a black Nissan in the intersection with major front-end damage, Hansen said.
One passenger in the Nissan was transported by ambulance to Sutter Delta Medical Center in Antioch in critical condition.
The driver of the Nissan and two passengers from the van were also transported to area hospitals, but information about the extent of their injuries was not immediately available.
The driver of the van was not transported, Hansen said.
Traffic is being diverted around the area while police investigate the crash, Hansen said.