HOUSTON -- A Florida senator is requesting that BP PLC share video from a September investigation of the stricken Macondo offshore oil well in the Gulf of Mexico, following revelations this week that an oil slick discovered last month floating in the Gulf of Mexico comes from the 2010 oil spill.

In a letter to BP CEO Bob Dudley, Democratic Sen. Bill Nelson asks the company to hand over the most recent video taken from inspections of the site. Meanwhile, BP says samples taken from an oil sheen first seen Sept. 16 show that the leaked crude comes from the wreckage at the site and not from the original Macondo well or the relief well drilled to stop the massive oil leak.

"Reportedly, you have sent down a remotely operated vehicle and concluded there is no leakage from the well," Nelson wrote. "Still, I am requesting that you immediately provide my office with all video from the September ROV inspection, as well as any subsequent inspections of the site."

BP acknowledged yesterday that the oil slick is leftover contamination from the Macondo well blowout and spill. But the company contends the leaked crude is very unlikely to have come from the well itself.

Rather, evidence gathered by investigators "strongly suggests" that the oil forming a sheen on the surface of the Gulf came out of the wreckage from the Deepwater Horizon drilling rig explosion, a BP spokesman says.

On Wednesday, the Federal On-Scene Coordinator (FOSC) overseeing the spill cleanup operation reported that the U.S. Coast Guard laboratory confirmed an oil sheen discovered near the spill site matches the oil that gushed out of the Macondo well. BP first reported the sheen to the Coast Guard after spotting it in mid-September.

BP insists that a recent investigation confirms the Macondo well and a relief well drilled to stop the leak are intact, suggesting the oil originated from equipment lying at the bottom of the ocean.

In an emailed statement, BP spokesman Brett Clanton said his company believes the oil most likely escaped from the bent riser pipe that collapsed after Transocean's Deepwater Horizon rig caught fire and eventually sank in 2010. Chemicals found with oil samples taken from the sheen point to this source, he explained.

"Like the Coast Guard, BP also has collected and analyzed sheen samples, which show a correlation with Macondo source oil but also indicate the presence of alpha-olefins, a compound found in the drilling mud but not in the source oil," Clanton said. "This strongly suggests the oil is emanating from the debris from the Deepwater Horizon accident."

The volume of the sheen, its location and the presence of drilling mud chemicals mixed in with the oil found in the sheen are all evidence that "the most likely source is the bent riser pipe that once connected the rig to the well head, where a mix of oil, drilling mud and seawater were trapped after the top kill operation," he added.

FOSC and the Coast Guard say they have yet to conclusively determine the source of the sheen, but those agencies also suspect it was formed by crude escaping the wreckage and not from any new leak or residual leakage.

BP says it is working with the Coast Guard to monitor the oil sheen, and the company says it is willing to work with Transocean to inspect the wrecked equipment lying at the bottom of the accident site if necessary. A Transocean representative said the company is monitoring the situation but maintains that BP is the responsible party tasked to work with the government on the problem.

"We will rely on the lab analysis as to the origin of the oil, and defer to the recent ruling of the federal court on the question of responsibility," said Lou Colasuonno, a Transocean adviser at FTI Consulting.

The Coast Guard says cleaning up the sheen is "not feasible" at this time. So far the leaked oil poses no risk to the Louisiana coastline and sensitive habitats there, they said.

Oil seeps naturally throughout the Gulf of Mexico each day, sometimes forming sheens at the surface but in low quantities that usually get quickly eaten by bacteria. But news of the continuing presence of crude oil and chemicals from the 2010 Gulf spill, the largest in U.S. history, is proof for environmental groups of the inherent risk to the oceans and coastal environments posed by offshore drilling.

Matt Dundas, campaign director at Oceana, said the incident is further proof that major accidents -- like the 5 million barrels leaked at the Macondo accident -- may never be fully resolved.

"Here we are, two-and-a-half years later, 5 million barrels of oil already spilled, and we're still dealing with this," Dundas said. "It's like a game of whack-a-mole. We can solve one problem and then another problem pops up, and then folks claim that we couldn't have predicted that other problem."

Hurricane Isaac's landfall at New Orleans in August exposed some crude oil from the 2010 spill that had earlier been buried by sediment. BP acknowledged the new pollution and pledged to clean it up (EnergyWire, Sept. 12).

Dundas argued that the public can expect pollution incidents from offshore drilling to arise even where there are no immediate indications of problems. Oceana advocates for more renewable energy generation, like offshore wind power, as an eventual replacement for fossil fuel use.

"We're never shocked when we hear that there's more oil showing up on the surface of the ocean near where offshore drilling operations are ongoing," Dundas said. "This to us is another strikingly disappointing example of the reality of the dangers of offshore drilling."