ST. SIMONS SOUND, Ga. (AP) — Rescuers were searching Sunday for four crew members of a cargo ship that overturned and caught fire near a port on the Georgia coast, the U.S. Coast Guard said.

The Golden Ray cargo ship ran into trouble in the early morning when it listed heavily in St. Simon Sound.

Of the 23 crew members and one pilot on board, the Coast Guard said 20 were safely evacuated from the ship, a 656-foot vehicle carrier. Search and rescue operations were ongoing for the remaining four crew members, with boat and helicopter crews assisting with the efforts. Local agencies also were helping with the rescue.

The Coast Guard said it was notified by a 911 call at about 2 a.m. of a capsized vessel in the sound. Petty Officer 3rd Class Ryan Dickinson said it isn’t clear if weather conditions caused the ship to lurch. Hurricane Dorian brushed past the Georgia coast last week before being downgraded to a post-tropical cyclone.

The cause of the incident remains under investigation.

The Golden Ray is flagged out of the Marshall Islands and was headed to Baltimore, according to the website vesselfinder.com. The ship’s registered owner is a South Korean company.

The Port of Brunswick is currently closed to vessel traffic, with an established emergency safety zone in St. Simons Sound. Vessels are not authorized within a half mile of the Golden Ray, which was lying on its side.

The port is one of the busiest U.S. seaports for shipping automobiles. Nearly 614,000 vehicles and heavy machinery units moved across its docks in the 2019 fiscal year that ended June 30, according to the Georgia Ports Authority.