TAMPA — An investigation of a human smuggling operation that was sparked by a traffic stop near Tampa earlier this year has resulted in three convictions, authorities said.

Federal agents charged brothers Jose Bartolo Calixto-Moran and Pedro Calixto-Moran, as well as Pedro's girlfriend, Marilu Ramirez-Bartolo.

They were the leaders of the operation, authorities said, and are Mexican citizens illegally in the United States. Pedro Calixto-Moran was sentenced to 71 months in prison; his brother to 41 months; and Ramirez-Bartolo to 27 months, a Homeland Security spokeswoman said Tuesday.

She estimated that the group, which was operating out of Arizona and Alabama, was smuggling more than 80 illegal aliens per month to various destinations across the country.

On Feb. 4, Hillsborough County deputies pulled over Kathleen Roberson, 21, of Phenix City, Ala., for driving a car without a license plate. She and 29-year-old Jessica Roland, also of Phenix City, were transporting five undocumented Mexican citizens to Immokalee.

Because they cooperated with the investigation, Roberson and Roland were not sentenced, authorities said.