OLYMPIA, Wash. -- The search resumes Wednesday morning for a missing WSDOT maintenance worker at the Hood Canal Bridge after the agency said his car apparently drove off the bridge.

Acting Secretary of Transportation Roger Millar sent an email to agency staff on Tuesday alerting them to the incident. He wrote that there were indications that the car of the employee, who has not been identified, breached a pedestrian cable railing on the lower deck of the bridge Monday night following the end of the employee's shift.

On Tuesday, crews used sonar equipment to scan the water and were able to identify what could be a car, far below the surface.

By Tuesday night, a private contractor brought in by WSDOT launched a remotely operated underwater vehicle to search the area where the water is between 300 and 400 feet deep, where the car may be located.

The underwater vehicle is equipped with cameras and operated by a crew onboard a boat that could be seen moving slowly beneath the Hood Canal Bridge just after 8 p.m.

The worker has not yet been identified, but Washington State Patrol has said was one of four people working on the Hood Canal Bridge on Monday. He was one the last one to leave, and he never made it home after his shift.

WSDOT said they have "high confidence" that the worker's personal vehicle went through a railing on a lower level of the bridge. That lower deck is designed for maintenance and is only used by WSDOT workers.

The Washington State Patrol, U.S. Coast Guard, Kitsap County Sheriff's Office, Kitsap County Fire and Rescue, and others were assisting in the search both the car and employee.