Reporting from Washington — A communications malfunction at a Wyoming Air Force base knocked 50 intercontinental ballistic missiles offline for 45 minutes last weekend as technicians scrambled to diagnose the problem, Pentagon officials said Tuesday.
The glitch in the underground cable system linking launch control centers at F.E. Warren Air Force Base to the missile silos affected one-ninth of the U.S. land-based intercontinental ballistic missile force, a key part of the nation's nuclear arsenal, officials said.
Officials stressed that there was no possibility the missiles could have launched accidentally, nor was there any indication that foreign governments or terrorists had hacked into the system. If the U.S. had needed to fire the Minuteman III missiles in the affected squadron during the outage Saturday, officials said, backup systems could have been used.
But the problem was considered serious enough that President Obama, Defense Secretary Robert M. Gates and Adm. Michael G. Mullen, the chairman of the Joint Chiefs of Staff, were notified. The White House declined to say when Obama learned of the incident, referring questions to the Pentagon.
"A particular piece of communications hardware" seems to be the most likely cause, said Lt. Col. John Thomas, a spokesman for the Air Force's Global Strike Command, which oversees the ICBM force. Thomas declined to specify the part, but said a similar malfunction was believed to have occurred a decade ago at the two other Air Force bases where ICBMs are based.
The communications failure meant that Air Force personnel responsible for ensuring the missiles' reliability received "error" messages and "launch facility down" warnings. The silos were hurriedly inspected to ensure that no one had broken in, one official said.
Officials held off disclosing the incident until Tuesday, in part because of sensitivity about publicly discussing problems with the missile launch system until the system could be examined.
But officials said that once it became clear the issue was technical, the military's level of concern dropped. "This was not insignificant, but at the same time it was not catastrophic," said one Pentagon official briefed on the incident.
Warren Air Force Base, outside Cheyenne, includes two other squadrons with 50 missiles each, officials said, and both remained fully operational. An additional 300 Minuteman IIIs at the Air Force bases in Montana and North Dakota also were unaffected by the glitch.
Besides the 450 land-based nuclear missiles, the U.S. has nuclear weapons that can be delivered by aircraft or submarine.
The backup systems that could have fired the offline missiles in an emergency were not activated Saturday because the nation was not on a high state of alert, officials said.
"The wartime capability of that squadron was never significantly affected," Thomas said.