The State Fire Marshal's Office says it could be months before an investigation reveals the cause of a Nov. 6 explosion that destroyed a Madison Township house.

In a statement released late last week, Columbia Gas of Ohio said the company is "confident that our main lines and service lines did not contribute to this incident" and will continue to support the fire marshal's investigation.

Kelly Stincer, a spokeswoman for the State Fire Marshal's Fire and Explosion Investigation Bureau, said the investigation by the bureau and the Madison Township Fire Department is still continuing into the origin of the blast and what caused it. She was unable to independently verify if Columbia might be liable for the explosion, saying it could be months before the bureau's investigation is completed.

"We anticipate this investigation to take some time," Madison Township Fire Chief Robert Bates said. "There are a number of technical resources needed to conduct a complete, thorough and accurate investigation of this incident."

Neighbors called emergency crews at 3:59 a.m. Nov. 6 to report an explosion in the 3300 block of Everson Road East, a Madison Township Police dispatcher said.

Stewart Bell, 59, who owned the home, was in a second-story bedroom when he was blown out of the house and landed in the driveway.

Bell's girlfriend, 54-year-old Shelly Williams, was also in a second-story bedroom when the home exploded. She was trapped under rubble and later died from internal injuries at Ohio State University Wexner Medical Center.

"I opened my eyes and saw a big fireball coming down," said Bell, who remembers lying stunned on the driveway outside his house.

"I lost everything I own and my girlfriend," he said shortly after being discharged from Ohio State University's Wexner Medical Center. "I wish it had been me instead of her."

The couple had known each other for 27 years.

Investigators ruled Nov. 7 that "an unspecified natural gas failure within the structure" had caused the explosion, said Lindsey LeBerth, a spokeswoman for the Ohio Department of Commerce's Division of State Fire Marshal.

Bell said he sometimes smelled gas outside his home. Last week, he bent down and tried smelling near the gas meter. He detected no odor there, he said, although he did smell gas in the area.

He said he didn't call the gas company because he didn't smell gas inside.

"I'm really, really regretting it," Bell said.

Columbia Gas spokeswoman Kelli Gaza Nowinsky said a neighbor reported a gas leak in July 2014 that was classified as a non-hazardous leak. It was repaired in February 2015.

That was the last time a leak was reported in the neighborhood, she said.

Inspectors with Columbia Gas routinely walk neighborhoods to complete leak surveys. The last conducted there was in April 2016. Nothing was detected at the time, Gaza Nowinsky said.

"This is the most important thing. If people think they smell natural gas, they have to call 911 and Columbia Gas," she said referring to a rotten egg smell that often accompanies leaks.

Upper Arlington case

Court-ordered mediation was to begin last week concerning the March 21, 2015, gas-line explosion in Upper Arlington that destroyed or damaged more than two dozen homes.

More than 30 plaintiffs are involved in 10 lawsuits against Columbia Gas, the cities of Columbus and Upper Arlington, a paving company and a consultant.

The Upper Arlington couple who owned the house that was destroyed was not home at the time and no one was seriously injured in that blast.

An investigation found that a Columbus water division worker opened an old gas line to the house that was incorrectly marked as a water valve. When the error became apparent, the worker did not fully close the valve and gas leached through the foundation.

The Public Utilities Commission of Ohio fined Columbia $200,000 after the company promised to accelerate a plan to precisely locate old and new lines and valves, check its records for any obvious location errors and open a training center to help emergency responders deal with gas-line hazards.