A recording of air traffic control officials in Colorado that was posted online appears to indicate a B-2 Spirit stealth bomber was experiencing engine trouble before it was force to conduct an emergency landing yesterday.

The Air Force is still investigating the B-2′s emergency landing Tuesday at the Colorado Springs Airport in Colorado, and has not yet said what may have caused it. But the recording, which was posted by the Facebook group Colorado Springs Crime Watch hours later that day, tracks the Colorado Springs tower’s discussions about the incoming aircraft and refers to an engine being out.

The B-2 was from the 509th Bomb Wing at Whiteman Air Force Base in Missouri, and was taking part in a routine training mission, the wing said.

B-2 Stealth Bomber emergency landing in Colorado Springs

Audio/Video: B-2 Stealth Bomber Emergency Landing at Colorado Springs Airport this morning. The aircraft crew called into Denver Center at about 3 am and gave them info that their number 4 engine was out and that they were about 10 minutes east of Colorado Springs but could not switch to Colorado Springs Airport frequencies to talk directly to them. They were initially going to come in on runway 17L but then came in from the south on runway 35R. They landed about 10-20 minutes later and AMR on scene provided the pilot with oxygen. The aircraft is most likely from the 509th Bomb Wing at Whiteman AFB, Missouri. Airport security was immediately ramped up for aircraft security. This audio/video is also posted on the Colorado Springs Crime News group. Feel free to share! #B2 #Stealth #Bomber #EmergencyLanding

Posted by Colorado Springs Crime Watch on Tuesday, October 23, 2018

The posted audio captures a controller from the tower at the airport relaying information to the Denver Air Route Traffic Control Center about the incoming B-2 experiencing an emergency. The controller says that he has called the fire department and equipment will be standing by when it lands.

The tower attempts to contact the B-2, and the controller says its aircrew is unable to change communication frequencies.

“I’m just relaying through Denver [Air Route Traffic Control] Center all of the information, but as far as I know, it is just the number 4 engine out,” the controller says in the recording. He says he is unable to talk to the aircrew, and says he planned to use a light gun to signal to them.

The B-2 landed safely, and both pilots were unharmed. The Colorado Springs Crime Watch group also said in the post that one or both pilots received oxygen after landing.

The 509th has not yet responded to an inquiry on whether an engine failed on the B-2.