By ANDRES VIGLUCCI AND ERIKA BERAS

A Cuban man trying to reach Florida on a speedboat with 32 others died Wednesday from head injuries he might have suffered when suspected smugglers tried to run from federal authorities in rough seas.

The man, whose name has not been released, was declared dead early Wednesday at Opa-locka Airport's Coast Guard station. He was airlifted to the station after cutters stopped the grossly overloaded 25-foot speedboat south of Key Largo late Tuesday. Miami-Dade Police said he was 35.

The Coast Guard also intercepted two smaller speedboats in the vicinity believed to have been involved in the smuggling operation. Federal authorities were holding seven suspected smugglers and 32 passengers in custody Wednesday while they investigate, the Coast Guard said.

The government would not say where they are being held. Cubans intercepted at sea are usually returned to Cuba, but in cases where fatalities have occurred some or all in a group can be brought to the United States to serve as witnesses in the criminal investigation.

''We are going to be conducting a thorough investigation,'' said Barbara Gonzalez, a spokeswoman for U.S. Immigration and Customs Enforcement. She declined to comment further, citing the incomplete investigation.

An aircraft belonging to U.S. Customs and Border Protection's air unit spotted two suspicious boats traveling together toward the Florida Keys at about 8:30 p.m. Tuesday, said agency spokesman Juan Muñoz.

Shortly afterward, the two boats were met by a third speedboat that apparently brought fuel, Muñoz said. Crew members were seen pitching fuel containers into the water, he said.

The Coast Guard dispatched three cutters. At some point, Muñoz said, the three suspect boats took off in different directions at high speed. The two smaller boats carried five suspected smugglers between them, said Petty Ofc. Jennifer Johnson, a Coast Guard spokeswoman.

All the migrants were on one boat, the largest, along with two suspected smugglers, she said.

The boat was stopped with no use of force at about 11:45 p.m., authorities said. Several passengers apparently had minor injuries, Muñoz said. One passenger was found to have severe head injuries.

Coast Guard officials said they're not sure how he was injured. In several other cases, migrants on boats have died or suffered serious injuries from falling or striking their heads as smugglers tried to elude capture at high speed.

''The seas were very rough last night, and going at high speeds in these conditions is very dangerous,'' Muñoz said. "Even experienced people suffer injuries in these conditions.''

After authorities stopped the vessels, Coast Guard officers provided aid to the injured man and called for a helicopter, where CPR was performed. Fire-rescue personnel pronounced the man dead at 3 a.m. Wednesday in Opa-locka.

Officials would not say why the man was not transported to a hospital south of Opa-locka.

Coast Guard Lt. Matt Moorlag said he would not second-guess the pilots' reasons for choosing to land farther north.

''Those determinations are made by aircraft personnel. I'm not going to speculate what was going on,'' he said.

Since December 2007, Moorlag said, 65 Cuban migrants have died at sea.

Miami Herald staff writers Andrea Torres and Jose Pagliery contributed to this report.