The bureau confirmed Saturday the flow of natural gas from the so-called A-7 well in the gulf was stopped by pumping in what it described as weighted drilling fluids.
"While the natural gas flow has stopped, there is additional work required to secure the well that includes setting barriers to ensure that no natural gas is released," the safety agency said in a statement.
The bureau said all of the people working on the drilling rig were evacuated as a security precaution. No injuries were reported.
It said it was notified of the leak Thursday by EnVen, a Kenyan energy company. The rig was leased by Rowan. an offshore drilling company with headquarters in Houston.
None of the companies involved in the incident issued statements regarding the release.
Rowan lists its Rowan-Louisiana rig as operating in 350 feet of water and leased to EnVen through April.