The Northrop N-9M crash-landed in the prison yard of the California Rehabilitation Center in Norco, Allen Kenitzer, a spokesperson for the Federal Aviation Administration (FAA) told Fox News on Monday.
Citing local authorities, the FAA said that only a pilot was onboard the single-engine aircraft. The condition of the pilot was not immediately clear.
It also was not immediately clear if any prisoners were in the yard at the time.
The plane, however, "sustained substantial damage," according to Kenitzer.
The FAA and the National Transportation Safety Board, which did not immediately return Fox News' request for comment, will investigate the crash.
The medium-security prison facility is located roughly 50 miles east of Los Angeles.
The Associated Press contributed to this report.