Reports surfaced Aug. 18 that a sheen of unknown origin was reported near the site of last year's oil spill in the Gulf of Mexico. BP officials, in coordination with the U.S. Coast Guard, deployed two submersibles to investigate the site.
BP said visual inspection indicated there wasn't any oil released from the Macondo well.
A gas explosion on the Deepwater Horizon oil rig killed 11 workers in April 2010 and resulted in a massive oil spill. Investigators said the process used to cement the Macondo well was part of the series of malfunctions that led to the explosion.
BP said during its inspection that it observed bubbles from cement ports near the site of its gulf wells.
"These observations are consistent with testing and sampling performed last year that detected nitrogen bubbles, a residual byproduct of the nitrified foam used in setting the wells' surface casing cement," the company said in a statement.
A reporter from the Press-Register newspaper in Mobile, Ala., took independent samples from the sheen and sent them to Louisiana State University for analysis.
Edward Overton, professor emeritus at LSU's environmental sciences department, told the Financial Times there was a "very, very close match" between Macondo oil and that taken from the slick in the Gulf of Mexico.