NEW ORLEANS (AP) — Underwater inspections at the site of BP’s Deepwater Horizon rig disaster have failed to identify the source of a persistent sheen on the surface of the Gulf of Mexico, officials said Tuesday.

The Coast Guard and BP both said the recent inspections confirmed that the company’s Macondo well, which blew out in April 2010 and spawned the nation’s worst offshore oil spill, remains secure and isn’t leaking oil. Relief wells that were drilled in 2010 to stop the gusher also were found to be secure during the four-day survey, BP said.