Three people, including a DCP Midstream LP employee, were injured Thursday after a fire broke out during routine maintenance on a natural gas gathering line in Colorado’s northeastern Weld County.

DCP spokesperson Rosslyn Elliott said the incident occurred at a PDC Energy Inc. well site. The Weld County Sheriff’s Office said two men were airlifted by helicopter and another was taken by ambulance to a nearby hospital to treat “various levels of burns.” The DCP employee was working with two contractors at the site near Highway 392 and Weld County Road 71.

PDC spokesperson Courtney Loper said the producer worked with first responders to shut-in nearby wells. She did not specify how many wells were affected by the fire, but the wells remained shut-in on Friday.

The cause of the incident remains unclear, said Elliott. DCP is conducting an internal investigation and cooperating with local authorities to “understand what happened.” The gathering line is now out of service.

The sheriff’s office was dispatched to the scene at 3:30 p.m. MDT and said preliminary information suggested the fire was caused by accident. The investigation is being handled by the Briggsdale Fire Protection District. 

DCP, one of the largest gas processors in the Denver-Julesburg Basin, during the third quarter reported record wellhead volumes of 863 MMcf/d. There were no informational postings on Friday that suggested an impact to broader operations in the region.

PDC has more than 95,000 net acres in its core Wattenberg field, where it targets the Niobrara and Codell formations. The assets continue to account for the bulk of the company’s production, making up 77,580 boe/d of 3Q2017 volumes of 92,500 boe/d.