USAF Lockheed U-2 Dragon Lady | U.S. Air Force photo
Lt. Col. Michael Meridith, a spokesman for the Air Force, confirmed the incident on Tuesday at the Air Force Association's annual conference outside Washington, D.C., but he didn't know the whereabouts or the condition of the service members. "It did crash," he said when asked if the plane went down. "Two pilots ejected."
Meridith said a search and rescue operation for the crew was under way.
The U.S. Air Force press desk later tweeted, "We can confirm a U-2 from @9thRW Beale AFB has gone down in Sutter County, CAA; 2 pilots have ejected; details to follow when available," referring to the 9th Reconnaissance Wing.
But officials walked back their initial statements on the pilots' condition as the day went on.
"We have no official confirmation on the pilots' condition," Beale Air Force Base tweeted later in the day. "We will provide updates when more information is available."
Air Combat Command around the same time issued a similar statement to correct a previous one that wrongly stated the pilots had "safely" ejected and were "awaiting recovery with aircraft in isolated area."
The U-2 Dragon Lady is a Cold War-era surveillance plane based at Beale Air Force Base in California. Trainer models of the aircraft hold two crew members.
This story has been updated.