An aircraft used by the Red Arrows display team has crashed at RAF Valley on Anglesey.
The Ministry of Defence confirmed it was a Hawk aircraft and said an air ambulance was sent to the scene at about 13:30 GMT on Tuesday.
It is understood two people were on board the aircraft and eyewitnesses said they saw them ejecting from the jet.
RAF Valley is a base used to train UK fighter pilots and aircrew.
An RAF spokesman said: “We are aware of an incident today at RAF Valley involving a Hawk aircraft.
“We are investigating the incident and it would be inappropriate to comment further at this stage.”
A Welsh Ambulance Service spokeswoman said it received a call about the crash just before 13:30 GMT and it sent an emergency ambulance and an air ambulance.
It is believed the aircraft was flying from RAF Valley, where training takes place for mountain and maritime operations, back to RAF Scampton, Lincolnshire – where they are based – when it crashed.
The Red Arrows are the RAF’s world-famous aerobatic team, performing stunts and daredevil displays in the distinctive Hawk fast-jets.
In total, about 1,500 service personnel, civil servants and contractors work at RAF Valley. Aircrews regularly visit the base to carry out simulation training.