The explosion in Creek County, Oklahoma, around seven miles south of Bristow occurred when two men were transferring oil-laced water from one 12-by-12 storage tank into another, said firefighter Mike Siler, who responded to the blast.
It was not yet clear what sparked the blast. Siler said the victim who survived was wearing welding gear and that the blast may have been triggered during welding operation, or possibly when a pump backfired.
The blast, which occurred around 11:30 am local time on Wednesday, was deafening and could be heard – and felt – for miles, according to local reports.
The man who survived was on the opposite side of the tank at the time of the blast and was said to be in stable condition on Friday.
The other man was “right at the bottom” where the blast occurred, Siler said.
“It had to have been instant. It was a bad deal for him,” he said.
The names of the victims were not available.
They were both employees of Wewoka, Oklahoma-based Cromwell Dozer & Backhoe Services, Siler said.
Plano, Texas-based Lapetco Incorporated operates the site.
The fire was extinguished within 30 minutes, though Siler said the site was difficult to access. Two trucks and a small patch of grass also burned.
The Occupational Safety and Health Administration is investigating.