Two people were dead and eight survivors were rescued from waters off the Florida Keys, U.S. Coast Guard officials said Friday.
Authorities said they were looking for another five people who are still in the water.
The Coast Guard said that 15 people, all thought to be migrants, were on board a rustic vessel on an illegal voyage.
The boat capsized about 14 miles south of Sugarloaf Key, and rescuers were informed about the migrants' distress about 10 a.m., the military branch said.
It was not clear from where they had traveled. U.S. Coast Guard officials said U.S. Customs and Border Protection was among the agencies that responded to the situation.
CBP spokeswoman Rob Brisley said by email that the incident off the Lower Keys remains under investigation. CBP has nothing more to add. The Coast Guard said people on a cruise ship saved a migrant. A photo of the scene released by the agency Friday shows Royal Caribbean Mariner of the Seas.
Rescues were also made by other good Samaritans and Coast Guard partner agencies in the area, it said in a statement Friday evening.
The deceased were pulled from the water by Florida Fish and Wildlife Conservation officers and transferred to a local medical examiner's office for identification, the Coast Guard said.
Among the eight rescued, two were in good health, but six others needed emergency medical attention, it said. Their conditions were not available.
The seas off Florida's southern coast are well known as a conduit for Cuban migration to the United States, and are now home to the largest exodus from the island since the Mariel Boat Lift of 1980.
Political turmoil and economic hardship, including inflation and a shortage of basic goods, are driving U.S. hopefuls into the Straits of Florida, according to experts.
It's a journey that regularly claims lives, made on dinghies, rafts and makeshift floatation devices.
Walter N. Slosar, the U.S. Border Patrol's Miami Sector, said on Friday that agents and other law enforcement officers have arrested 108 Cuban migrants at 12 landings in the Florida Keys in the last two days.
Last month, CBP reported that its agents, with the help of the Coast Guard, rescued 23 migrants in waters off Marathon, Florida. CBP, the Coast Guard and local law enforcement agencies rescued 38 Cubans stranded on the remote Florida Keys islands in June, according to a CHP statement.
In the agency's statement, Rear Adm. Brendan McPherson, commander of the Coast Guard's southeastern operations, said that Cuban migrants are often found at sea without life jackets on unseaworthy or overloaded boats and homemade rafts. The search continues for others that may have survived this tragic incident, he said.