[Updated at 7:47 a.m.] The company that owns the rig that exploded, Transocean Ltd., said most crew members are safe.

"A substantial majority of the 126 member crew is safe but some crew members remain unaccounted for at this time," the company said in a statement.

The company describes itself as the "world's largest offshore drilling contractor and the leading provider of drilling management services worldwide" and says it has 140 offshore drilling units.

[Posted at 7:04 a.m.] At least 11 people were missing and seven were critically injured after an explosion on an offshore oil rig 52 miles southeast of Venice, Louisiana, in the Gulf of Mexico, the U.S. Coast Guard said Wednesday.

At the time of the explosion Tuesday night, there were 126 people on board the rig, said Coast Guard Senior Chief Petty Officer Mike O'Berry.

Four helicopters and four Coast Guard vessels were in the area searching for the missing people, he said.