****UPDATE****

Authorities are investigating a natural gas explosion in rural north Texas that killed one utility worker.

Officials are trying to find out how a utility crew hit a large natural gas line Monday afternoon, sending a massive fireball into the area.  Johnson County's emergency management coordinator, Jack Snow, says officials want to know if the gas line was marked before the blast.

The federal Occupational Safety and Health Administration is among numerous agencies investigating.

The lone utility worker missing after the blast was found dead Monday night, once searchers could safely walk through the entire charred area.  Authorities had hoped the missing man had left the scene on his own, like some of his colleagues who drove themselves to hospitals.

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A giant plume of fire was burning after an explosion in a rural area near Cleburne in north central Texas,
and at least 10 people were reported missing.

Cleburne city manager Chester Nolen tells Dallas-Fort Worth television station WFAA that Monday's explosion left at least 10 people missing, and a city fire official said at least six were injured.

A witness in nearby Granbury tells The Associated Press she was about 8 miles from the site of the explosion. She says she heard a "huge rumbling" that she thought was thunder and then a tornado.

Television images showed a large fireball and a burned out vehicle and construction equipment.