Ted Poszywak, left, chief of the Frederick-Firestone fire department, and public information officer Summer Campos, right, take questions from members of the media during a news conference, while standing next to a picture of the location where an unrefined gas leak explosion killed two people inside their home in Firestone, Colo., Tuesday, May 2, 2017. Poszywak said that an investigation has revealed that the April 17, 2017 explosion was caused by unrefined natural gas that was leaking from a small abandoned pipeline from a nearby well owned by Anadarko Petroleum. (AP Photo/Brennan Linsley)

Ted Poszywak, left, chief of the Frederick-Firestone fire department, and public information officer Summer Campos, right, take questions from members of the media during a news conference, while standing next to a picture of the location where an unrefined gas leak explosion killed two people inside their home in Firestone, Colo., Tuesday, May 2, 2017. Poszywak said that an investigation has revealed that the April 17, 2017 explosion was caused by unrefined natural gas that was leaking from a small abandoned pipeline from a nearby well owned by Anadarko Petroleum. (AP Photo/Brennan Linsley)

FIRESTONE, Colo. (AP) — A home explosion that killed two people in Colorado was caused by odorless, unrefined natural gas leaking from an old pipeline, investigators said Tuesday, prompting the governor to order statewide inspections of similar lines.

The underground line was believed to be out of service but was connected to a well within 200 feet (60 meters) of the house, fire investigators said. The line had been cut about 10 feet (3 meters) from the house, state regulators said.

Gas seeped through the ground and into the basement, where it exploded on April 17, investigators said.

Officials said they do not yet know why the line was connected to the well, or when and how it was cut.

Gov. John Hickenlooper 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.

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“Public safety is paramount,” he said.

He didn’t give details of the inspections but said energy companies will be required to perform pressure tests, where the lines are sealed up and pressurized, so that any leaks will register as a drop in pressure.

It was not immediately known how many flow lines the state has or the distance they cover.

Colorado Oil and Gas Conservation Commission Director Matt Lepore, the state’s top industry regulator, said operators are required to tell the commission the planned route of their flow lines, but the state does not have a record of all the lines ever installed.

Lepore said a line taken out of service — formally considered abandoned — is supposed to be disconnected and sealed at both ends and all flammable gas is supposed to be removed.

He said regulators do not yet know whether this line had never been disconnected from the well, or if it had been disconnected but later reconnected for some reason.

The well, owned by Anadarko Petroleum, was shut down all of 2016 but resumed production in January, state records show. The records do not show the reasons, and Anadarko has previously declined to comment on specifics of the well, citing the ongoing investigation.

Although Anadarko owns the well, investigators said they do not know who was responsible for the unused pipeline. The well was drilled in 1993 and had previous owners before Anadarko.

The well has been shut down, and officials say they don’t believe any neighboring homes are in danger.

The nearby homes were built after the well was drilled. Lepore said the pipeline that leaked was cleanly cut, which he said could mean it was severed by construction equipment while the neighborhood was being built.

The state will investigate whether anyone broke laws or regulations in connection with the unused line, Hickenlooper said.

The explosion occurred in Firestone, about 30 miles (48 kilometers) north of Denver.

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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.

Ted Poszywak, chief of the Frederick-Firestone fire department, said the 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. Because the gas leaking into the home had not been refined, it had no odor, Poszywak said.

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

Anadarko CEO Al Walker said the company is cooperating with the investigation and suggested it would be watching closely. He said company officials want to make sure they understand the reasons for the fire department’s findings and to ensure “no stone is left unturned prior to any final determinations.”

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.

The investigation’s 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 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.

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Associated Press Writer Thomas Peipert contributed to this report.

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Follow Dan Elliott at http://twitter.com/DanElliottAP. His work can be found at https://apnews.com/search/dan%20elliott.