LONDON - A new oil sheen was spotted in the Gulf of Mexico, although energy company BP said Thursday the discovery had nothing to do with its operations and was far from the site of its disaster-hit Macondo well.

A spokesman for another company involved in investigating the sheen said he believed it had already dissipated since being first spotted last week.

BP spokesman Daren Beaudo said his company had sent several remotely controlled mini-submersibles into the water over the weekend to investigate the source of the sheen - a shiny coating that floats on the surface of the water and generally comes from leaked or spilled oil - but had concluded "that it couldn't have been from anything of ours."

A statement from BP PLC placed the site of the sheen near two abandoned exploration well sites in the Green Canyon Block in the Gulf of Mexico, although its size wasn't disclosed.

The sheen was 172 miles (277 kilometers) from BP's Macondo well and about 100 miles off the Louisiana coast.

The company's account differs from an anonymous report received by the Coast Guard's National Response Center over the weekend, which says that a semisubmersible sent down to a plugged and abandoned well on Saturday determined that it was leaking. The report, which was called in to the center Sunday evening, names BP as the suspected responsible party. It says that the equipment captured footage of a release, and that remedial actions would be determined based on the results of the sampling.

The U.S. Bureau of Ocean Energy Management, Enforcement and Regulation confirmed that the report was associated with the incident.

But Beaudo told the AP that the initial report may not be accurate. He said the company tested the cloudy water near the wellhead and believes the substance was silt from the Gulf floor.

On Wednesday, another discharge of crude oil was reported in the Green Canyon Block, according to federal records. That one was the result of heavy rain washing oil into the water from an Exxon Mobil platform, according to the report.

According to an online map published by the U.S. Department of Energy, the Green Canyon Block - a massive area of water south of Louisiana - is south and west of the Mississippi Canyon Block where the Macondo well blew up.

A U.S. government official also said the area around Macondo was clear.

"They are not investigating any sheens in the vicinity of the BP well," Paul Barnard, Operations Controller for the New Orleans sector of the Coast Guard, told The Associated Press on Thursday.

BOEMRE said Thursday that the agency is currently working with operators in the Gulf to determine if the light sheen was associated with any abandoned wells in the area.

Reports of oil sheens are common in the Gulf of Mexico, where oil and gas production, ship traffic, natural seeps, and abandoned and plugged wells all can contribute to the problem. On Wednesday, the National Response Center - the government's storing house for oil and chemical spills - received reports of 13 sheens off the Louisiana coast. Many are never investigated and disappear before someone can determine what caused them.

The Coast Guard said Thursday that several sheens reported in the past two weeks were determined to be either natural seepage or federally approved releases.

In 2010, anonymous callers reported 210 spills or sheens in the Green Canyon area, which covers several thousand square miles. About a quarter of the calls described "unknown sheens," without a known source. More than half - 112 of those reported - originated from platforms, but many of the reports are unverified.

The AP has reported that at least 27,000 abandoned oil and gas wells in the Gulf are not routinely inspected when plugged or subsequently monitored for leaks.

But reports of sheens now garner much more attention after the Gulf oil spill.

The catastrophic April 2010 explosion at the Macondo well killed 11 men and led to the worst offshore oil spill in U.S. history. The stricken well spewed more than 200 million gallons of oil before it was capped some three months later.

BP's operations in the Gulf of Mexico have seen particular scrutiny following the disaster and it remains the area's largest leaseholder, but other energy companies have operations in the Gulf as well.

Among them is Shell, which is still investigating the cause of a recent oil spill in the North Sea - the area's worst in a decade. The Dutch company counts several projects in the Gulf's Green Canyon Block.

Shell did not immediately return a call seeking comment Thursday.

Rick Rainey, a spokesman for the energy services firm Enterprise Products Partners L.P., said the U.S. Coast Guard had asked his company to check one of its pipelines in the Green Canyon area over the weekend because of the sheen.

"We spent the last few days inspecting our lines. Everything's fine with the line," he said. "What I understand from our guys who have heard from the Coast Guard is that the sheen has since dissipated."

There were about 80 active leases on drilling sites at the end of June in the Green Canyon area, according to a quarterly bulletin published by the Bureau of Ocean Energy Management, Regulation and Enforcement. BP holds 10 of those leases. Other holders include Royal Dutch Shell PLC, Chevron Corp., Anadarko Petroleum Co., and numerous other smaller companies.

A spokesman with Exxon Mobil Corp. said company officials were looking into the matter. Chevron did not immediately respond to AP calls for comment.

Associated Press writers Janet McConnaughey and Bill Fuller in New Orleans, Toby Sterling in Amsterdam, Dina Cappiello in Washington and Harry R. Weber in Miami contributed to this report.