Coast Guard Senior Chief Petty Officer Mike O'Berry says the first blast was reported at 7 p.m. CDT Tuesday.
Later, the rig sent an emergency signal. O'Berry says a nearby rig at the same time reported the Deepwater Horizon was in flames. He says the rig didn't ask for help during the initial call. The Coast Guard sent help after the emergency signal came.
The Coast Guard is investigating what happened during that three hours.
A spokesman for the rig owner says any logged events are part of the investigation.
Seventeen workers are hurt, 11 missing and more than 100 escaped.
