At approximately 7:45 pm CDT, on 20 April 2010, high-pressure methane gas from the well expanded into the marine riser and rose into the drilling rig, where it ignited and exploded, engulfing the platform.[36][37] Eleven missing workers were never found despite a three-day U.S. Coast Guard (USCG) search operation and are believed to have died in the explosion.[38][39] Ninety-four crew members were rescued by lifeboat or helicopter, 17 of whom were treated for injuries.[36][40] The Deepwater Horizon sank on the morning of 22 April 2010.