The train was stopped at 701 E. New Dock Street near Terminal Island in San Pedro.
Personnel on scene could not immediately shut off a leaking valve.
The leak was reportedly from a small tanker of unleaded gas.
A "top-loader" machine lifted the tanker off the rail car, and the tanker's cap was tightened and the leak secured. Firefighters spread foam on the
One person was reportedly treated by medical personnel on scene, but that person left on their own.
The report of a hazardous-materials spill was received by the L.A. City Fire Dept. at 4:08 p.m., according to spokesman Erik Scott.