Air National Guard F-16s were scrambled on Sunday from Maryland -- causing a sonic boom heard throughout large portions of Washington, D.C., and the surrounding area -- to investigate an aircraft that had entered a restricted area, a U.S. official told ABC News.

Authorities were concerned about the plane, which was unresponsive and flying a strange flight path over the D.C. area, a second U.S. official said.

The jets, which were deployed from Joint Base Andrews, saw that the pilot of the aircraft had passed out, this official said. The plane subsequently crashed.

Aircraft that are scrambled in this way are under the control of NORAD, and another U.S. official said that NORAD was operating in support of the Federal Aviation Administration.

A flight tracking website shows the craft had made it to its initial destination, Long Island MacArthur Airport in New York, but appears not to have landed -- instead heading back toward the D.C. area.

A fourth source said that the White House and U.S. Capitol were put on high alert but not "red alert," which would have triggered an evacuation.

The plane, a Cessna Citation, crashed around 3:30 p.m. ET in southwest Virginia, the FAA said in its own statement, which did not provide details on the pilot's condition.

Virginia State Police were searching Sunday but had not yet recovered anything, they said.

ABC News' Clara McMichael and Sam Sweeney contributed to this report.

This is a developing story. Please check back for updates.