A collision between a barge and a double hulled oil tanker may have spilled as much as 11,000 barrels of crude oil into the Sabine-Neches Waterway near Port Arthur, Texas. The oil spill is being called the biggest in the state since 1991.

The oil spill occurred when a barge collided with the 807-foot double hulled tanker Eagle Otome, sending as much as 11,000 barrels of oil into the waterway. A voluntary evacuation recommendation was issued to the 57,000 residents of the town. According to a Reuters report, about a dozen people did evacuate, but were back in their homes on Sunday.

State and environmental agencies are coordinating the clean up of the spill. According to Reuters, the spill is contained by several booms intended to prevent it from spreading, and the Sabine-Neches Waterway is expected to remain closed for at least five days. The Wall Street Journal is reporting that approximately 500 people and 15 skimmers were on hand for the cleanup. As of Sunday, about 1,100 barrels of oil had been recovered.

The Eagle Otome was on its way to Exxon Mobile Corps.’ Beaumont refinery on Saturday when the collision occurred. According to Reuters, the barge was one of two being moved by the Dixie Vengeance tug boat. The cause of the collision is unknown, and is being investigated by the U.S. Coast Guard and the National Transportation Safety Board.

The Sabine-Neches Waterway is used by four U.S. refineries in east Texas to transport their supply of oil. According to Reuters, the four facilities have a combined refining capacity of 1.15 million barrels, equal to about 6.5 percent of total U.S. capacity.