A search mission launched after a survivor said he was one of a group of migrants who left the Bahamas on Saturday.
Rescuers from the United States Coast Guard are searching the waters off Florida’s Atlantic coast for 39 people reported missing for several days after a boat believed to be used for human smuggling capsized.
A good Samaritan alerted the Coast Guard early on Tuesday after rescuing a man clinging to the mostly submerged hull of the boat after it hit bad weather about 72km (45 miles) east of the town of Fort Pierce, the maritime security agency reported on Twitter.
The survivor told authorities that he had left the Bahamas’ Bimini islands with 39 other people on Saturday night, and that they had not been wearing lifejackets, the Coast Guard added.
Cutter vessels and aircraft have been deployed to search an area stretching from Bimini to Fort Pierce to find the missing.
The Coast Guard said it was treating the incident as a case of suspected human smuggling.
The nationality of those on board is not yet known.
Migrants have long used the islands of the Bahamas as a stepping stone to reach Florida and the United States, with the Bimini Islands only about 80km (50 miles) east of Miami.
Smugglers typically try to take advantage of breaks in the weather to make the crossing, but the vessels are often dangerously overloaded and prone to capsizing. There have been thousands of deaths over the years.
The latest accident follows another ill-fated crossing last week when the authorities rescued 32 people whose boat capsized west of Bimini, Coast Guard spokesperson, Petty Officer Jose Hernandez told the Reuters news agency.
Most of those attempting the crossing come from Haiti and Cuba.
At least 557 Cuban migrants in all have been picked up at sea by the Coast Guard since October, according to the agency.
Crossings by Haitians have also grown more frequent as the Caribbean island nation deals with economic and political crises, as well as gang-related kidnappings.
The Coast Guard said it had intercepted at least 159 Haitian nationals this fiscal year.