OAKLAND -- A 12-year-old Oakland autistic boy who was hit by at least one car while walking in traffic early Friday morning on eastbound Interstate 580 at Fruitvale Avenue remained in critical condition Friday afternoon, a California Highway Patrol spokesman said.

The boy, whose name was not released, is in a medically-induced coma at Highland Hospital in Oakland, authorities said. He was initially believed to be 16 or 17 years old but CHP spokesman Officer Sam Morgan said he was simply big for his age.

The boy's family reported him missing to Oakland police shortly before he was injured.

He was wearing orange pajama bottoms and a white shirt when he was struck by the vehicle and did not have identification on him.

He walked into at least two different lanes of traffic on the freeway before he was hit, CHP spokesman Officer Daniel Hill said.

The collision caused other cars to crash, injuring three people and closing the freeway for more than an hour, authorities said. All three people in the cars were taken to the hospital with either minor injuries or complaints of pain, Hill said. Four cars were damaged.

All eastbound lanes were shut down for a time but were reopened by 7:45 a.m.

Anyone with information is asked to call the CHP at 800-835-5247 or 510-450-3821.

Bay Area News Group staff writer Mark Gomez contributed to this report.