At least 22 Haitian migrants died after their boat capsized in shark-infested waters near the Turks and Caicos Islands, the US Coast Guard has said.
At least 73 of the 150 people believed to have been on board were rescued, but more than 50 are still missing.
Several of the victims appeared to have been bitten by sharks, officials said.
A police boat from the islands, north of Haiti, were trying to tow the sinking boat to port when it capsized.
The incident occurred at 0420 (0920 GMT) about half a mile (0.8km) south of Providenciales Island, a spokesman for the Coast Guard in Miami said.
Sixty-three people were immediately picked up by the police vessel and taken to South Dock on Providenciales.
Ten others were later saved by the police after a US Coast Guard helicopter spotted them clinging to the 25ft sail freighter's hull.
The helicopter also located a number of bodies in the water, some of which appeared to have been attacked by sharks.
"We have reports that some did have bites that appeared to be from sharks," US Coast Guard Petty Officer Barry Bena told reporters.
"We don't know how many."
The Turks and Caicos Islands, a British overseas territory, is located to the north of Haiti and south-east of the Bahamas.
The most commonly seen sharks in the area are nurse, lemon, Caribbean reef, and blacktip sharks. According to experts, the lemon and reef sharks occasionally are of danger to humans.
The number of Haitian migrants attempting the dangerous crossings to the US or to other Caribbean islands has increased in recent months.
Some 909 Haitians have been caught by the US Coast Guard since January, officials say.