A series of natural gas pipeline explosions in Midland County, Texas sent five people to hospital with critical burn injuries, and interrupted energy pipeline operations in the area, officials said, Reuters reports.

The region is the home to the Permian Basin, the largest U.S. oilfield, and is crisscrossed by oil and gas pipelines. The cause of the explosion and fire were not immediately known.

Five workers with critical injuries were airlifted to University Medical Center in Lubbock, Texas, and were being treated at the center’s burn unit, said University Medical Center spokesman Eric Finley.

Pipeline operator Kinder Morgan said on Wednesday it had isolated a portion of its El Paso Natural Gas Pipeline (EPNG) as a precaution, after being alerted to the fire near its line. One of its employees was injured and taken to hospital, spokeswoman Sara Hughes said.

“There was a third-party pipeline involved that also experienced a failure, and preliminary indications are that the third-party line failure occurred before the EPNG line failure,” Kinder Morgan’s Hughes said in an email.

The company is investigating the cause of the fire and evaluating any damage to its property. Regulatory agencies and customers were notified of the incident, she added.

“Fire Department personnel suppressed the fire, however approximately one hour later a second and third small explosion followed,” said Elana Ladd, public information officer for the city of Midland, in emailed comments.

Multiple pipelines are located near the site, Ladd said, adding that first responders were focusing on shutting off pressure and flow to the pipelines at the site.

The pipeline explosion occurred on a rural road, FM 1379, about five miles south of Highway 158 at around 11:30 a.m. local time (1630 GMT), Ladd said, adding that the road had been closed.

No further information on the injured was immediately available.

Ladd identified one of the injured as a firefighter

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