FIRESTONE, Colo. (AP) — A home explosion in Colorado that killed two people was caused by odorless, unrefined natural gas leaking from a small pipeline that was considered abandoned but was still connected to a nearby well, fire officials said Tuesday.

The line had been cut open some distance from the well, allowing gas to leak into the soil and make its way into the basement of the home, said Ted Poszywak, chief of the Frederick-Firestone fire department.

A third person was badly burned in the April 17 explosion in Firestone, about 30 miles (48 kilometers) north of Denver.

Investigators do not know why the line remained connected to the well, or how or when it was cut and began to leak.

The line was 1 inch (2.5 cm) in diameter and reached within about 6 feet (1.8 meters) of the house, Poszywak said. It was buried about 7 feet (2.1 meters) underground.

The house was within 200 feet (60 meters) of the well, but the fire chief stressed it was the pipeline and not the well that leaked. The well has been shut down, and officials say they don't believe any neighboring homes are in danger.

Anadarko Petroleum owns the well, but it has had previous owners since it was drilled in 1993. Nearby homes, including the one that exploded, were built after the well was drilled.

Poszywak said investigators are trying to determine who is responsible for the line that leaked.

Gov. John Hickenlooper on Tuesday ordered inspections and tests of all active and abandoned gas pipelines within 1,000 feet of occupied buildings. The pipelines are called flow lines and carry gas from wells to storage tanks or other collection points.

The state will also investigate whether anyone broke laws or regulations in connection with the abandoned line, Hickenlooper said. The Firestone Police Department is investigating the deaths.

Mark Martinez and Joseph William Irwin III were killed. Erin Martinez, who was married to Mark Martinez, was badly burned. Irwin was her brother.

Neighbors told the Longmont Times-Call the two men were working on a water heater in the home's basement at the time of the explosion.

Poszywak said the two men were not responsible for the explosion.

Natural gas is odorless when it comes out of the ground, and energy companies add a smell during refining so leaks will be noticeable. Since the gas leaking into the Firestone home had not been refined, it had no odor, and no one in the house would have detected it, Poszywak said.

The findings are sure to renew a long-running debate in Colorado over safe distances between homes and oil and gas facilities, and whether local governments should be allowed to impose tougher regulations than the state.

Fast-growing Colorado cities sometimes overlap with highly profitable oil and gas fields. The Legislature killed a proposal this year that would have increased the minimum distance between schools and new oil and gas facilities.

The state Oil and Gas Conservation Commission regulates the distance between new wells and existing structures, but local governments set the distance between new homes and existing wells. In Firestone, the minimum distance is 150 feet.

State records show the well near the home that exploded was shut down all of last year and resumed production in January, although the records do not show the reasons. Anadarko has previously declined to comment, citing the ongoing investigation.

The well was last inspected in 2014 and received a "satisfactory" rating.

Anadarko and Great Western Oil & Gas said last week they would shut down and inspect more than 3,060 similar wells as a precaution during the investigation.

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