Princess Kate has paid a heartfelt tribute to the three Royal Navy crew members who died today after a helicopter crashed during a training exercise. Debris was scattered across the grass in Sourton Down near Okehampton after the Merlin helicopter came down in a training exercise in the early hours of the morning.Witnesses reported hearing a 'loud explosion' and an 'almighty flash of red' amid the tragedy.General Sir Gwyn Jenkins, the First Sea Lord and Chief of Naval Staff, confirmed the three deaths and sent his 'deepest condolences' to the crew's family and friends. Meanwhile, Princess Catherine has taken to X to say both she and William had the family and friends of the deceased in their 'hearts at this very difficult time'. She wrote: 'I was so saddened to hear of the tragic loss of three service personnel from the Fleet Air Arm following a helicopter training exercise last night. 'William and I hold their families and friends in our hearts at this very difficult time.'The Daily Mail understands that she and The Prince of Wales will be contacting the families of those who lost their lives directly in the coming days. Her father-in-law King Charles III is also aware of the crash and will write privately to the families, it is said. The site of the crash - which shut several local roads including the A30 - is between the Royal Navy's air bases at Yeovilton in Somerset and Culdrose in Cornwall.It is also close to Okehampton battle camp, a military facility on the edge of Dartmoor used for training Merlin helicopter crews from the Commando Helicopter Force. Princess Kate has paid a heartfelt tribute to the three Royal Navy crew members who died today after a helicopter crashed during a training exercise today A drone photo shows the scene of the Royal Navy helicopter crash at Sourton Cross today Princess Catherine has taken to X to say both she and William had the family and friends of the deceased in their 'hearts at this very difficult time'. The 'C' initial shows she wrote this message personallySir Gwyn, the head of the Navy, said this afternoon: 'I am deeply saddened to share the news that three crew members onboard a Royal Navy Merlin Mk4 helicopter have died after it crashed in the early hours of this morning near Sourton, Devon.'I know this will come as a huge shock to all in our Naval community, and my deepest condolences go out to the families, friends and loved ones impacted by this tragedy.'I would like to thank Devon and Cornwall Police and the search and rescue teams who responded to the incident this morning. An investigation is under way.'He added that further updates would be provided 'in due course'. Police were called to the scene just before 4am and the cause of the incident remains unknown.The Ministry of Defence said the families of the personnel killed in the incident have been informed. Defence Secretary John Healey said he was 'devastated' at the three deaths of personnel who 'served with excellence and will be much missed'.A Ministry of Defence spokesperson said: 'It is with deep sadness that we can confirm three members of the Royal Navy have died during a helicopter training exercise on Wednesday, June 3 near Sourton, Devon.'The families of the service personnel have been informed and have requested a period of grace before further details are released. Our thoughts and sympathies are with their families and friends at this sad time.'At Prime Minister's Questions today, Sir Keir Starmer said he was 'aware of a Royal Navy helicopter crash this morning in Devon', adding: 'This will be a deeply worrying time for the families and more information will be set out as soon as possible.'Residents who live nearby claimed to have heard a 'loud explosion' at about 3.15am. One local told the Daily Mail: 'Two helicopters last night flew so close to my house that the windows shook and my children were woken by it.'Others in the village were also disturbed by it. We semi-regularly have these flights but nothing has been as close or loud or dangerous feeling as last night.'Another claimed to have heard a helicopter 'flying very low'. Several road closures were in place around the A386 and A30 Sourton Cross slip and services area.A further witness, who lives less than a mile from the crash site but who didn't want to be named, said she was awoken about 4am by a loud noise.She said: 'It sounded as if the helicopter was not right as it flew over the house. It was so low it almost took the roof of the house off. The house really shook and there was a huge bang shortly afterwards. 'We get a lot of loud noises here and I didn't think too much about it at the time. It was only when we got up an hour or so later that we found the roads swarming with emergency vehicles.'And when we looked over the hill you could see the charred remains of the helicopter. You could tell it was a helicopter because you could identify the tail rotor.'Everything else was in bits and so don't know how anyone could have escaped. The land was scarred by the accident and wreckage strewn over the field.'