Two contract workers were injured, one critically, while conducting Atmos Energy’s “routine maintenance” work Monday on a pipeline near a Dallas Design District apartment complex.

Dallas Fire-Rescue spokesman Jason Evans said crews were dispatched shortly after 3:45 a.m. to an incident near the Alexan Riveredge Apartments.

In an emailed statement, Atmos said its contractor was performing maintenance on a pipeline near the complex when they experienced a “worksite event.” Evans said the pipeline “somehow exploded during the process.”

Dallas Police Department officers responded about 4:07 a.m. to the 100 block of Turtle Creek Boulevard to assist with traffic control, according to DPD spokesman Jonathan Maner.

Two workers near the explosion were taken to a hospital, where one remains listed in critical condition as of Monday afternoon while the other has already been discharged, Evans said.

According to Evans, there were no other reported injuries and no impact to the apartment building or neighboring businesses.

The maintenance involved testing the line with air and not natural gas, the company said, and there was no damage to the pipeline or impact on natural gas access to the area.

NBC5 reported the apartment complex was evacuated in early September due to a gas leak. Atmos didn’t comment to The Dallas Morning News on whether the incidents were related.