The train, which began its journey in Chicago, was carrying about 35,000 gallons of ethanol, a corn-derived alternative fuel blended in gasoline, the Tampa Bay Times reported.
Gary Sease, a spokesman for CSX Transportation, estimated about 4,500 gallons spilled from three cars.
The engineer and conductor, the only people on the train, were not hurt.
The derailment of 11 of the train's 81 cars occurred at about 1 a.m. as the train approached the port. Sease said the ethanol was contained to the area immediately around the train, although stormy weather made the task difficult.
The crash was in an industrial area, where employees were unable to come to work. The port was expected to be closed for most of the day because equipment needed to clear the wreck had to be brought in from Atlanta.
"We saw all the lights and we couldn't go in. We didn't know what happened," Rene Delgado, a welder superintendent, told the Times. "That's 10 hours of work that we miss today. We don't go in and we don't get paid."