About 20 Cuban migrants are clinging to the a lighthouse in the water about 20 miles from Key West.
U.S. Coast Guard officials are trying to talk the migrants into coming down from the lighthouse, the Miami Herald reported.
Chief Petty Officer Ryan Doss said that multiple federal agencies will determine whether the lighthouse is dry land under the so-called "wet-foot, dry-foot policy" that holds with Cuban migrants, who can stay and pursue citizenship if they reach U.S. land.
The 109-foot structure is submerged in about 10 feet of water. The Miami Herald identified the structure as the American Shoal lighthouse off Sugarloaf Key.
Doss says the migrants swam from a homemade vessel that they sailed from Cuba to the lighthouse Friday morning when they saw the Coast Guard approaching.
Ten years ago, U.S. authorities sent home 15 Cubans who landed on an abandoned Keys bridge because they said it constituted land. A federal judge later ruled that decision was illegal.
Some of the group eventually made it to land in the Keys on another attempt.
The Miami Herald reported that the Coast Guard on Friday set up a 1,000-yard safety zone around the lighthouse.
“Our biggest concern right now is safety,” Doss said, according to the newspaper. “We’re trying to get them down and make sure they are okay.”
Some migrant are up so high up on the lighthouse that Coast Guard officials are unable to tell their gender.
“Some of them are way up there,” said Doss.
The Associated Press contributed to this report.