Officials unsure if oil still flowing in Gulf after explosion

The massive explosion is still being investigated, a process that may be complicated by the fact the mobile offshore drilling rig sank beneath the surface on Thursday. The sinking also raises the potential for pollution, officials said.

Meanwhile, U.S. Coast Guard search and rescue teams were continuing to search for 11 missing workers. Officials said workers who were evacuated from the site said the 11 may have not been able to get off the rig after the explosion.

The drilling rig was operated by the Swiss company Transocean. Adrian Rose, a vice president at Transocean, said the rig was in the process of plugging and abandoning the well in preparation for development by BP, which owns the leasing rights.