Maj. Bob Bromage said there are possible minor injuries in the two-vehicle accident. He said the vehicles have been moved to the side of the road.
The eastbound left lane of U.S. 278 is blocked as first responders work the accident, the alert said.
Weather and onlookers are adding to the delays.
Google maps reported a 18-minute delay on the eastbound lanes of the Hilton Head bridge around 4:30 p.m.
Westbound lanes were backed up past the Hilton Head Plantation entrance to Beach City Road.