On the morning of May 9, a small single-engine plane crashed in northern California in the United States, killing both of the people onboard, local media reported.

The Piper Cherokee went down in rough terrain at about 10:50 a.m. local time at a site about 5 miles (8 kilometers) near the Livermore Municipal Airport, it was reported.

Ian Gregor, a U.S. Federal Aviation Administration (FAA) spokesman, said the cause of the crash is still unknown.

FAA investigators are heading to the crash site and the National Transportation Safety Board (NTSB) is also planning to investigate, local CBS 5 television station quoted Gregor as saying.