Interior, Coast Guard probe 10-mile Gulf of Mexico sheen

“Shell has no current indication that the sheen originates from wells in either the Mars or Ursa projects,” spokeswoman Kelly op de Weegh said.

But she added that out of “prudent caution” the company has activated the Louisiana Responder, a Marine Spill Response Corporation (MSRC) skimming vessel. The MSRC is a nonprofit spill response organization that formed in response to a 1990 oil spill control law.

The company is also seeking air monitoring. “Shell has also requested flights to monitor the 1-by-10-mile sheen closely with additional aerial surveillance,” the spokeswoman added. “At this time, the source of this sheen is unknown, and Shell’s priority is to respond proactively, safely and in close coordination with regulatory agencies.”

A Coast Guard spokesman said a “pollution investigator” is surveying the sheen Thursday morning.

“We have an overflight going out to take a look at it,” said Petty Officer Jeremy McClure in New Orleans. “We will know more when they report back to us.”

The Shell projects are both located about 130 miles southeast of New Orleans in the Mississippi Canyon region of the Gulf of Mexico.

Reports of the sheen come just ahead of the two-year anniversary of the beginning of the BP oil spill.

Transocean’s Deepwater Horizon rig — which was drilling BP’s Macondo prospect — exploded on April 20, 2010, killing 11 workers.

The blown-out Macondo well, which like the Shell projects is in the Mississippi Canyon region, poured over 4 million barrels of oil into the Gulf over several months before it was capped.

This post was updated at 8:57 a.m.