The Coast Guard said they suspected it was an undertaking of human trafficking.
The rescued man told officials that he had left Bimini in the Bahamas with 39 others on Saturday night and encountered bad weather that caused the boat to capsize.
According to the survivor, no one on the ship was wearing a life jacket.
The US Coast Guard Southeast told CNN that so far the Coast Guard is the only agency engaged in rescue efforts. The search area extends 45 miles east of Fort Pierce Inlet to Bimini.