The Department of Interior’s Bureau of Safety and Environmental Enforcement was “taking steps” Thursday to identify the source of a “light sheen” sighted in the central Gulf of Mexico (GOM) said to be about 10 square-miles-long. The sheen was reportedly spotted near the Mars and Ursa deepwater production units, both operated by Royal Dutch Shell plc.

According to reports, the sheen was first reported by federal officials to Shell, because the sheen was floating between its Ursa and Mars natural gas and oil platforms, which are 130 miles southeast of New Orleans in the Mississippi Canyon. BP plc is Shell’s partner in Mars, while BP, ExxonMobil Corp. and ConocoPhillips are its partners in Ursa.

Following a subsea inspection, Shell confirmed late Thursday that there were “no well control issues” associated with its drilling operations in the area.

“Shell has no current indication that the sheen originates from its wells,” spokeswoman Kelly op de Weegh said. However, because of “prudent caution,” the producer activated the Louisiana Responder, a Marine Spill Response Corp. skimming vessel, for the “orphan sheen.” Shell estimated that the spill contained about about 6 bbl of oil. Both Ursa and Mars remained in operation.

According to the BSEE, Shell deployed remote operating vehicles to inspect the infrastructure and seafloor, including permanently plugged wells in the area and a known natural seafloor seep that was found near the sheen. The company was seeking air monitoring over the area and “requested flights to monitor the…sheen closely with additional aerial surveillance…”

A pollution investigator was dispatched to the area by the U.S. Coast Guard, according to Petty Officer Jeremy McClure. More information was expected once a flyover of the area had been completed.

Shell produced on average 180,000 boe/d net in the GOM last year, it said Thursday.

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