US oil group Chevron said Tuesday it had shut down a pipeline off the coast of Louisiana in the Gulf of Mexico to investigate a "potential leak."

"Chevron Pipe Line shut down the Main Pass System this morning to investigate a potential leak," the company said in a note to its clients seen by AFP.

That led to the subsequent shutdown of the Cypress pipeline system, as the Main Pass system was "the only connecting pipeline system currently providing volumes into Cypress," it said.

An incident report available on the website of the National Response Center, dated Monday, says 1,075 gallons (about 4,000 liters) of crude may have seeped into the Gulf.

Chevron did not say how much oil might have leaked.

Last year, an explosion on the Deepwater Horizon oil rig killed 11 workers and sent 4.9 million barrels of oil streaming into the Gulf before the well was capped three months later, causing widespread environmental damage.