DENVER – Oil and gas operators in Colorado appear to be complying with state-ordered inspections of thousands of pipelines after a natural gas explosion blamed on a severed line killed two people inside a home, regulators said Friday.

All but a few small energy companies submitted reports by a May 30 deadline on their inspections and locations of oil and gas flow lines, said Todd Hartman, spokesman for the Colorado Oil and Gas Conservation Commission, which regulates the industry.

Flow lines connect wells to storage tanks and other collection points. The state has processed information associated with more than 16,500 wells, Hartman said. The state estimates there are 116 oil and gas operators in Colorado, which ranks seventh nationally in natural gas production.

The state ordered inspections and locations of above-ground flow lines within 1,000 feet (300 meters) of buildings after the April 17 explosion in the town of Firestone, about 30 miles (50 kilometers) north of Denver. Investigators blamed the explosion on odorless, unrefined gas from a small severed pipeline near the home.

The state also required inspections of all flow lines to verify that any abandoned lines are clearly marked and capped pending a permanent sealing of the line.

Operators must test all flow lines for leaks by June 30. That involves closing the lines, pressurizing them and monitoring for any loss of pressure. Commission Director Matt Lepore has warned that wells connected to pipelines that haven’t been inspected could be shut down.

As of Friday, the agency had processed reports from all of the largest oil and gas firms operating in Colorado and will contact any firms that missed the deadline, Hartman said.

Fire investigators said the Firestone explosion was caused by odorless, unrefined gas spewing from an old underground pipeline. The 1-inch (2.5-cm) line was believed to be out of service but was still connected to a producing gas well owned by Anadarko Petroleum.

The line had been cut about 10 feet (3 meters) from the home and the gas seeped into the basement, investigators said. Authorities have not said why the line was still connected to a well or how it was severed.

The explosion and another fatal blast that killed a worker at a small oil tank farm in nearby Mead intensified a debate over regulating the oil and gas industry in Colorado. Dozens of fast-growing neighborhoods have overlapped with the busy Denver-Julesburg field north of Denver, prompting concerns about health and safety.

Anadarko and Nobel Energy, the state’s two largest gas producers, say they expect to meet the June 30 testing deadline.

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Associated Press Writer Dan Elliott contributed to this report.