British oil giant BP said Thursday it has sealed a steel containment dome believed to be the source of a new oil sheen first spotted last month near the site of the disastrous 2010 BP oil spill in the Gulf of Mexico.

"Initial visual inspections of the cap and plugs have observed no oil droplets emanating from any of the openings," BP said in an announcement, adding that it will continue to monitor the sheen through satellite images "for several days to confirm that the cap and plugs are secure."

The equipment, an 86-ton steel container called a cofferdam, was used in the early stages of the response to trap oil and methane hydrates from a leaking drill pipe in an attempt to funnel it to the surface.

BP used a remotely-controlled underwater vehicle to inspect the Gulf bottom and the wellhead area at the site, after the most recent oil sheen was reported to the Coast Guard's National Response Center on Sept. 16, after it was observed on satellite images, according to media reports.

BP also said Thursday that it has inspected the well and two nearby relief wells and confirmed that they aren't leaking. The wells were permanently sealed in September 2010, and BP said the most recent inspections were the third time the seal's integrity has been confirmed.

The 2010 blowout of BP's Macondo well in the Gulf of Mexico triggered an explosion that killed 11 rig workers and unleashed the worst oil spill in US history.