HOUSTON -- An oil slick floating on the surface of the Gulf of Mexico near the site of the 2010 oil spill is not coming from that stricken well, officials announced yesterday.

Representatives from BP PLC and the federal government issued notices yesterday afternoon that a survey of the Macondo well site by a remotely operated vehicle (ROV) confirmed that the well, plugged with cement two years ago, is secured and is leaking no oil. Relief wells drilled to contain the leak are also secure, they said.

BP also said yesterday that the source of the sheen appears to be an 86-ton steel containment dome, or cofferdam, that was first used in attempts to stanch the flow of crude oil and siphon some of it to the surface.

A U.S. Coast Guard lab recently found that samples of the sheen showed crude oil that matched the crude from the Macondo well, which is estimated to have spewed roughly 5 million barrels of crude oil in the 2010 spill.

"The latest survey marks the third time since the Macondo well was permanently sealed in September 2010 that it has been visually inspected at the sea floor and confirmed not to be leaking," BP reported. "The nearly three-day-long inspection was also successful in identifying the cofferdam, a piece of containment equipment used during the Deepwater Horizon response, as the probable source of the surface sheen."

BP conducted the survey with the help of Transocean, the company that owned and operated the Deepwater Horizon semi-submersible drilling rig.

The ROV inspection was performed under the oversight of a handful of government agencies, including the Coast Guard, the Bureau of Safety and Environmental Enforcement, the Bureau of Ocean Energy Management, and the Federal On-Scene Coordinator (FOSC) for the spill response. Representatives from the states of Louisiana, Florida and Mississippi were also invited to view the operation, BP says.

FOSC estimates that the containment dome, which was moved away from the Macondo well but left on the bottom of the ocean, is leaking less than 100 gallons of oil per day, at a rate of "approximately 15 globules per minute."

Officials caution that the oil seen leaking from the containment dome must be tested to determine if it is indeed the source of the surface oil sheen, which was first spotted by BP and reported to the Coast Guard on Sept. 16. Two samples have been taken to labs for analysis, one for the government and the other for the two companies to share.

The Coast Guard currently says that the sheen poses no threat to any coastline, and that cleaning it up would be infeasible. But there is still no word on whether any attempt will be made to stop the leakage from the containment dome.

"The Coast Guard is further evaluating what is believed to be seepage from the containment dome to determine how best to respond," said FOSC office chief Capt. Duke Walker in a release.

Leaks from the cofferdam were detected at the top and on one side.

BP says it thoroughly ran an ROV over the full length of the crumpled 4,500-foot-long riser pipe originally thought to be the source of the sheen and found no evidence of leaking oil.