Shell says the leak was not from a well on the ocean floor. That is what happened in the massive 2010 BP oil spill. This drilling site was in the same Mississippi Canyon region as the BP spill and is some 7,300 feet deep.
The Coast Guard says the problem was reported Sunday and that the leaking line was connected to a vessel supplying the drilling fluid. It says more than half of the leaking fluid was oil.
The Southern Environmental Law Center says the drilling is part of an exploration plan challenged in federal court.
Shell says federal environmental officials approved a plan to temporarily stop drilling and make repairs.