Four South Koreans are unaccounted for after a cargo vessel capsized off the coast of Georgia in the U.S. on Sunday morning.

The U.S. Coast Guard said it launched a rescue operation after receiving a report at around 2 a.m. Sunday that the Golden Ray, a car carrier, had capsized in the St. Simons Sound near the city of Brunswick.

The ship had 24 people on board, including 13 Filipinos, ten South Koreans and an American pilot. 

An official at the South Korean consulate in Atlanta said that 20 people were rescued, while four South Koreans are unaccounted for.

Later on Monday, a ministry official said U.S. Coast Guard members will mobilize to rescue the four Koreans at 7:30 p.m. The four are presumed to be in the engine room of the ship, and responded to tapping from rescue workers outside the hull.

Coast guard officials said smoke and flames on board the ship delayed the rescue of the four South Koreans.

The Golden Ray, which belongs to Hyundai Glovis, the logistics arm of Hyundai Motor Group, was reportedly carrying about four-thousand vehicles at the time of the accident.