Crews have deployed more than 12,000 feet of boom to contain oil along the side of the river near Port Arthur, the Coast Guard said. Nine oil-skimmers and three vacuum trucks are also collecting oil.
Precautionary booming was placed around the environmentally sensitive Bessie Heights Marsh area. There have been no reports of the oil affecting wildlife.
The spill occurred early Monday when a barge struck and pierced the starboard fuel tank of the Danish-flagged tanker Torm Mary, which was anchored for a routine refueling operation. Remaining fuel was transferred to an undamaged tank.
The Coast Guard's marine safety office is investigating the accident.