CLEBURNE, Texas (CBSDFW.COM) - An investigation is underway by the National Transportation Safety Board after a small plane crash in Cleburne that left two people dead Thursday afternoon.

According to the NTSB, an American Aviation AA-1A airplane left Cleburne airport during the afternoon but never landed back, which led relatives of the two people on-board to call authorities.

The NTSB said the aircraft was found at around 10:30 p.m. Thursday evening in a flat field about 3.5 miles away from the airport. Officials believe it may have crashed at around 5:20 p.m.

The two victims have not yet been identified.

The NTSB went to the scene to investigate the crash. A cause is unknown at this time.