Trooper Rick Conn suffered third-degree burns, Kentucky State Police said. He was in fair condition late Monday, said Kathy Cosco, a spokeswoman for Cabell-Huntington Hospital in West Virginia.

Kenneth Reid, Annabelle Reid and Charles Reid were treated at Our Lady of the Way Hospital in Floyd County and released, a hospital spokeswoman said. Their conditions were not available Monday night.

Derek Newsome, Jeannie Newsome and Alexis Newsome were taken to Highlands Regional Medical Center in Prestonsburg, where they were released late Monday, and James Fulks was sent to the University of Kentucky Medical Center, a hospital spokeswoman said. Fulks' condition was not available.

Terry Hall was taken to Pikeville Medical Center, Trooper Scott Hopkins said. His condition was not available Monday night.

Sgt. Phil Crumpton, a state police spokesman in Frankfort, said Conn was on his way to work at the Pikeville post when he smelled gas coming from the Floyd County subdivision where he lives. He was driving when the blast occurred, and the explosion blew out the windows in his cruiser. Conn was injured but continued toward the homes to help evacuate them, Crumpton said.

"He heard a call for help and pulled a woman and small child out and then collapsed," Crumpton said. "I heard he's in good spirits. He's got burns on the face, neck, chest and hands."

By late afternoon, all the house fires were out, Crumpton said, but authorities were still waiting for the gas pipeline to burn out.

The cause of the blast was not known.

Officials from the federal Office of Pipeline Safety were en route to the scene. They would have to wait for the blaze to burn out to begin their investigation, said spokesman Damon Hill in Washington, D.C. Investigators should be able to determine quickly if the line was tampered with, he said.

"If it's third-party damage, we can identify that normally fairly quickly," Hill said. "If it's some other type of mechanical error, it could possibly take up to a month or so."

The 4-inch line carrying natural gas liquids to a processing plant exploded about 8:30 a.m., said Stacy Floden, spokeswoman for the Kentucky Emergency Management Agency.

Floden said the high-pressure gas line belonged to Kentucky-West Virginia Gas Co. Kentucky-West Virginia Gas is a division of Equitable Gas in Pittsburgh, according to David Spigelmyer, a spokesman for Equitable Gas.

He confirmed that the company owns the line but said it is operated and maintained by another company - Mark West.

Cory Bromley, spokesman for Mark West Hydrocarbon in Colorado said the company believes it operates the pipeline. The cause of the explosion, he said, is unknown, and the company probably won't know it for some time, because the pipeline is underground. He said valves on either side of the rupture had been shut off.

Mark West Hydrocarbon Inc. is an owner of Mark West Energy Partners, which is engaged in the gathering, transmission, processing and marketing of hydrocarbons and the marketing of natural gas and natural gas liquids, according to the company's Web site.