The body of a man believed to be John J. Long, of Alameda, California, was found floating Saturday afternoon near his 55-foot (17-metre) sailboat near the town of Puerto Madero, just north of Mexico's border with Guatemala, embassy spokeswoman Judith Bryan said.

Long had sent a distress signal from the boat, 'Culin,' which bore Irish, Mexican and US flags, Ms Bryan said. The US Coast Guard confirmed its Alameda centre had received an alert.

Authorities in Puerto Madero told the US embassy that the boat may have had electrical problems and could have been headed for Panama, she added.

Mexican police and marines were investigating whether the boat was linked to organised crime or drug trafficking, after they discovered a false bottom, presumably for cargo, said an official with Mexico's navy who asked not to be named for security reasons.

He added that Long was found with bruises all over his body.

Residents of a nearby town saw two people carrying suitcases walk off the boat toward shore, said Saul Gomez, head of a local fishermen's group.

Two people were detained in connection with the incident, state police spokesman Bernardo Gomez said, although it wasn't immediately clear if they were the same pair who allegedly fled the boat.

Long was born in Ireland but was a US citizen, Ms Bryan said.

Mexican authorities found a US passport with his name and picture on the boat.

The 'Culin,' a 48.5-foot (15-metre) recreational vessel, is registered under Long's name in Alameda, according to the Web site Boatinfoworld.com, which collects public records.

A spokesman for the California Department of Motor Vehicles found no boat listed under a registration number published by Mexican media, but said a 12-foot Sea King Runabout has been registered to Mr John J. Long of Alameda since 1992. -- AP