The leak was caused when the tanker collided with two barges being towed by a tug boat, according to a US Coast Guard officer.

The clean-up operation has already begun. Over 46,000 gallons of oil had already been removed from waters by Sunday night.

Fifteen skimming vessels sailed the area recovering the oil, and workers dropped more than 45,000 feet of boom to keep the oil from spreading. More than 500 people were involved in containing and cleaning the spill, over the weekend.

The spill has caused the temporary closure of Port Arthur, as well as the nearby Sabine Neches Waterway. It remains unclear as to when the port, about 100 miles east of Houston, Texas, will reopen or when crews will finish the clean-up.

No injuries were reported when the Exxon Mobile-chartered tanker -- the 807-foot Eagle Otome -- collided Saturday with the barges. The tanker was carrying about 570,000 gallons of crude oil to Exxon's Beaumont refinery when it crashed. The cause of the crash was unknown, but is under investigation.

Port Arthur is primarily for industrial use, but it is not far from wetlands. None of the nearby marshes or sensitive wildlife were adversely affected, but one heron was described as being "oiled." The bird is alive and undergoing treatment.