DENVER (AP) — An oil and gas company has reactivated more than 1,350 wells in northern Colorado that were shut down last year after a fatal house explosion blamed on a severed pipeline.

Anadarko Petroleum said Tuesday it inspected and tested pipelines connected to the wells before returning them to service.

The company shut down hundreds of wells after the April 17, 2017, explosion killed two people, injured a third and destroyed a house in the town of Firestone, about 30 miles (50 kilometers) north of Denver.

Investigators said the explosion was caused by odorless, unrefined natural gas from a pipeline that was severed about 10 feet (3 meters) from the house. The line was believed to be abandoned but was still connected to one of Anadarko's operating wells with the valve turned to the open position, investigators said.

The investigation is still underway.

Anadarko permanently shut down and plugged 600 wells after the explosion. About 1,050 more remain shut down while the company decides what to do with them, Anadarko said.

The company did not have an estimate on how much petroleum or revenue it was losing while the wells are idle.

Anadarko said last year the combined daily output of the 3,000 wells it shut down after the explosion was the equivalent of 13,000 barrels of oil. That would be about 546,000 U.S. gallons (2.1 million liters).

Anadarko said three wells in the neighborhood where the house exploded remain turned off and will eventually be plugged and permanently shut down. That can't happen until litigation surrounding the explosion is settled, the company said.

Anadarko said it bought a house beside the explosion site in a settlement with the owner. The house was damaged by the blast.

The pipe blamed for the explosion was a flow line, a type that carries oil and gas from wells to nearby equipment. Colorado has hundreds of thousands of flow lines.

After the explosion, Colorado regulators adopted new rules for installing, testing and shutting down flow lines. They also require energy companies to report the locations of many pipelines to regulators.