Two missileers at an Air Force missile alert facility in Nebraska were sent to a hospital Tuesday for minor smoke inhalation after a piece of electrical equipment near their underground launch control center overheated.

F.E. Warren Air Force Base in Wyoming said in social media posts Tuesday that its 90th Missile Wing — which operates 150 Minuteman III intercontinental ballistic missiles around the clock — responded to an emergency at a missile alert facility outside of Harrisburg, Nebraska, at about 3:40 p.m. Tuesday.

The base said the fire departments of nearby Banner County and Gering, Nebraska, responded immediately and found a piece of electrical equipment had overheated and produced smoke.

The missile alert facility — the hub of ICBM operations, which contains underground launch control centers where missileers wait to launch nuclear missiles, if called upon — was evacuated when the equipment began smoking.

Second Lt. Nikita Thorpe, a spokeswoman for the 90th, later said in response to an Air Force Times query that the smoking equipment was in the underground equipment building that is adjacent to the launch control center. Thorpe said an investigation is underway and details on the equipment could not be released.

“An investigation is ongoing to determine the root cause of the incident,” Thorpe said. “In the meantime, we can assure the public that these systems are well-maintained and constantly inspected and monitored for safe operations. A detailed assessment by our expert maintenance and safety personnel is in progress.”

The two missileers in the launch control center center were taken to the Regional West Medical Center in Scottsbluff, Nebraska, for treatment of minor smoke inhalation. Thorpe said they were subsequently released.

Thorpe said that a redundancy built into the Minuteman III’s design ensured its safety and operational readiness remained uninterrupted while the missileers were taken to the hospital.

“The safety of our airmen and their well-being are always a priority, and we will continue to monitor their status,” the 90th said in a Facebook post.

UPDATE 3: Two active duty members have been transported to Regional West Medical Center in Scottsbluff for treatment of...

Posted by F. E. Warren Air Force Base on Tuesday, April 10, 2018

Additional information was not immediately available from the 90th.

“The public was never in danger, and the safety and security of the Minuteman system was never in doubt,” Col. Matthew Dillow, vice commander of the 90th, said in a Facebook post. “We would like to thank the outstanding local community first responders for providing such rapid support. Their professionalism and swift response were key to the safe resolution of the incident.”