Twenty people have been safely removed from a 656-foot vessel named the Golden Ray after it became disabled on the St. Simons Sound off the coast of Brunswick, Georgia, around 2 a.m. Sunday, Coast Guard officials said in a release.
The number of people on board included 23 crew members and one pilot, four of whom have not been accounted for. It is currently too risky to go inside the vessel to search for the missing, Coast Guard officials said at a press conference Sunday afternoon.
The missing crew members' last known location was the engine room, but they could be elsewhere on the ship by now, U.S. Coast Guard Lt. Lloyd Heflin told ABC News. The entire crew is from South Korea, Heflin said.
Once the vessel has been determined to be stable, rescue crews will carve out a plan for the best way to enter the ship, officials said.
The cargo ship is currently "listing heavily" on the sound, according to the Coast Guard. Images show the carrier lying on its side on the water.
The Port of Brunswick has been closed for the search, and vessels are not permitted within half a mile of the overturned ship, which is visible from shore.
Black smoke could be seen coming off the starboard side of the ship when the fire first began, officials said. Visible flames and smoke are no longer emitting from the vessel, but officials have been unable to determine whether the fire has been completely extinguished.
The Georgia Department of Natural Resources, Moran Towing, SeaTow, Brunswick Bar Pilots Association and Glynn County Fire Department are assisting in the search.
It was not clear what caused the boat to list or whether any of the rescued crew were injured.
ABC News' Nicholas Cirone and Ben Stein contributed to this report.