Air Vice Marshal Montol Suchookorn says an investigation team has been sent to the scene of Monday morning’s crash in Chaiyaphum province. The area is about 220 miles (350 kilometers) northeast of Bangkok.

He said he was unable to confirm reports the jets had collided.

The planes were taking part in Exercise Cobra Gold, an annual joint Thai-US military exercise in which personnel from Singapore, Japan, Indonesia, South Korea are also taking part.