MIAMI (REUTERS) - Police who found five pounds (2.26kg) of pot during a routine traffic stop searched the motorists' house and followed the scent to an empty backyard swimming pool where 82 marijuana plants were growing beneath a thick slab of concrete, officials said on Friday.

Miami-Dade police arrested two men and a woman, all Cuban-born, and charged each with manufacturing and trafficking marijuana, as well as grand theft for stealing electricity from the local utility to power the lights that were shining on the growing plants.

On January 23, police smelled marijuana after they stopped two of the men, Valexy Quintero-Consuegra, 37, and Marley Torres-Denis, 27, in a Range Rover for not wearing seat-belts, according to an arrest affidavit.

The two were overheard discussing what to tell the officers about five pounds of marijuana in the car's trunk, police said.

The second man, Eddy Pelaez-Ramirez, 44, told police he had nothing to do with the car and gave detectives permission to enter his house in Homestead, a rural community about an hour south of downtown Miami.

Police said they "detected a strong odour of marijuana" and found a hidden trap door leading to the plants beneath the pool.

Indoor marijuana farms called "grow houses" are more prevalent in Florida than any other United States state, with 540 uncovered by law enforcement in the state in 2012, according to the Drug Enforcement Administration.

Florida voters in November will decide whether to legalise medical marijuana after activists collected more than 700,000 signatures.

The Florida Supreme Court last week approved the measure after a challenge from Attorney General Pam Bondi.