Kanawha County Commission President Kent Carper was on the scene with emergency officials and said the extent of the damage was unknown, as was the cause.
Carper said flames were shooting at least 175 feet into the air when he arrived on the scene. The heat from the fire charred the asphalt in the north and southbound lanes of Interstate 77, causing the road to crumble. The extreme heat melted the steel guardrails and was melting vinyl and aluminum siding on houses hundreds of feet from the blast site, he said.
"There were still some hotspots going 30 minutes after the gas was shut off," Carper said.
There were concerns about the fumes that could have been produced by the extreme heat, but Carper said recent rainy weather conditions were "just right" to prevent that.
"This was our Christmas miracle," Carper said. "If this had happened at night or during rush hour, it's hard to tell how many fatalities we would have had."
Miller said a secondary search for injured persons would be conducted Tuesday evening.
"We'll go board by board and brick by brick," he said. "Anything we find out there could potentially be evidence."
An emergency shelter was set up at Aldersgate United Methodist Church along Kanawha County Route 21 in the community of Sissonville.
Shelter director Pat Taylor said only a few people were using the shelter as of 3 p.m., but he expected more as the evening wore on.
At least one woman was taken to the hospital for smoke inhalation and shortness of breath.
Taylor said the woman, 65, lived near the explosion site and walked into the shelter coughing.
"She was in need of some dry clothes - I'm not sure how she got wet," he said.
There are about 4,000 miles of gas transmission lines in West Virginia, plus thousands more miles of smaller gas lines.
Transmission lines are the largest of gas pipelines. They take highly pressurized gas across long distances.
Since 2002, there has been one injury and $11.5 million in property damage because of incidents at transmission lines in West Virginia, according to the federal pipeline administration.
Columbia Gas-owned pipelines in the state have been involved in 10 "significant" incidents, which involve $50,000 or more in damage or at least one hospitalization.
Nationally, the leading cause of pipeline accidents is third-party damage - often those are lines being struck by an incautious contractor.
But one of the most recent large explosions in the country occurred because of oversights by a pipeline's owner, according to federal investigators.
In fall 2009, a 30-inch transmission line ruptured in San Bruno, Calif., killing eight and injuring many more. It also destroyed 38 homes and damaged 70 others. After a yearlong investigation, the NTSB concluded Pacific Gas and Electric Co. overlooked or ignored industry standards.
Writers Jared Hunt and Ry Rivard contributed to this report.