All four people on board a small plane that crashed in California Saturday are dead, according to the Tulare County Sheriff’s Office.

The identities of the victims have not been confirmed. It is unknown what led to the crash.

Around 6:35 p.m. Saturday, deputies were called to the area of Road 68 and Avenue 288 near the Visalia Airport in Visalia, California, for a possible downed plane, authorities said.

When deputies arrived, they found a single-engine Beechcraft Bonanza had crashed, killing all on board.

The National Transportation Safety Board ​said Sunday it is investigating the crash.

ABC News California affiliate KFSN reported the plane crashed just a few seconds after taking off.