BALTIMORE, DEC. 21 -- Two former Miami firefighters and another Florida man have been convicted in federal court here in a scheme to ferry $400,000 a month in high-quality cocaine from Miami to Baltimore by car and train.

A jury returned the verdicts Thursday before U.S. District Judge J. Frederick Motz. The three men, who face up to 80 years in prison and $4 million in fines each, will be sentenced in about six weeks. Each faces a minimum of five years' imprisonment.

The men, convicted of both conspiracy and possession with intent to distribute more than 500 grams of cocaine, were identified as Nathaniel Dennis, 34, a former Miami fire department lieutenant; former firefighter Larry Deleveaux, 29, and Rudolph Jackson, 28.

Prosecutors capped the case after another firefighter, Harry Franklin Payne, 30, pleaded guilty to lesser charges in the case and agreed to cooperate with authorities, according to Assistant U.S. Attorney Stephen L. Purcell. Payne faces a possible sentence of 20 years' imprisonment and $1 million in fines.

Drug Enforcement Administration investigators said Dennis recruited Deleveaux and Payne to transport cocaine from Miami to Baltimore where Jackson and Deleveaux were believed to have drug underworld connections.

In what became a regular delivery service in late 1986 and early 1987, according to the DEA, the couriers drove rental cars from Miami to Baltimore, dropped off the drugs and flew back to Miami.

Last spring, couriers began to feel the heat of Operation Pipeline, a highway surveillance program organized by East Coast state police, and switched to rail , making the 23-hour Miami-to-Baltimore run by Amtrak, according to the DEA. On April 2, after being spotted by Amtrak police and put under surveillance, Payne was arrested as he alighted in Baltimore.