NASSAU, Bahamas — Haitians fleeing their impoverished homeland met tragedy when their boat went down off the Bahamas, killing at least 20 people and leaving only three known survivors, including an alleged migrant smuggler, authorities said yesterday.

Survivors said the boat was carrying 24 people when it capsized Saturday night, according to a U.S. Coast Guard spokesman in Miami, Luis Diaz. Just before dawn Sunday, fishermen heard screams.

Volunteers searched for bodies, tying life preservers onto them so they could be recovered by the U.S. Coast Guard, Chris Lloyd of the Bahamas Air Sea Rescue Association said.

“We recovered as many as we could,” Mr. Lloyd said.

The migrants appeared to be aiming for American shores. The accident happened less than 150 miles from Miami, Chief Petty Officer Ralph McKinney of the Royal Bahamas Defense Force said. The boat had set out from Nassau and was supposed to stop in Bimini en route to Florida, he said.

Two Haitian survivors, a man and a woman , were being treated at a Nassau hospital for dehydration. The third survivor, a Honduran marine mechanic, was taken into police custody as authorities investigate smuggling allegations, Mr. McKinney said.

The two Haitian survivors identified the Honduran as the sunken vessel’s captain, Mr. Lloyd said.

The Haitian Ambassador, Louis Harold Joseph, said he had not yet received confirmation that everyone who died was Haitian. But he expressed doubt that the voyage was connected to recent Haitian food riots in which at least seven people died.

He said he was talking to leaders of the Haitian community in the Bahamas to see if they could help identify the victims or provide information about the voyage. But he said he didn’t expect much.