The US air force says maintenance errors by three airmen damaged a nuclear-armed missile in its silo in 2014, triggering an accident investigation, the Associated Press reports.
The news agency says the accident occurred on May 17, 2014, but the air force only explained the consequences on Friday (local time) after questions by the Associated Press.
The air force released a statement and brief summary of the investigation results, and said the accident had not put public safety at risk.
AP reported that the air force refused to provide details of the accident, saying they were classified.
The launch site is operated by the 320th Missile Squadron of the 90th Missile Wing in a remote area of northeastern Colorado, the news agency reported.