A Royal Marine trainee has collapsed and died on an exercise in Dartmoor, the Ministry of Defence (MoD) has confirmed.
The man, who has not been named, was based at the Commando Training Centre at Lympstone, Devon, and was taking part in a 30-mile march.
An MoD spokesman said the cause of death was unknown.
He said: “This incident is being investigated and the thoughts and sympathies of the Naval Service are with the family and friends of this man.”
The man died on Thursday during the so-called “30-miler” march across upland Dartmoor, the last major test undertaken as part of the 32-week Commando course.
Trainees must navigate the route themselves and complete it within eight hours while carrying additional safety equipment.
The MoD said the name and details of the man who died were not being released, at the request of his family.
In July 2013, army reservists Edward Maher, Craig Roberts and James Dunsby died after collapsing during an SAS training exercise in the Brecon Beacon in Wales.
A number of other soldiers taking part in the programme that day, when temperatures hit 29C (84F), also collapsed and needed medical attention.