Update 5.53pm: All Army cadets evacuated from a mountain in Co Down following bad weather are safe, a spokesman said.
A group of more than 50 from the Cleveland Army Cadet Force in Middlesbrough were on a training exercise in the Mourne range in Co Down when they got into difficulties on Wednesday.
Children as young as 12 were among those rescued. Five suffered ankle injuries after slipping on wet stones and a number were treated for the effects of exposure, the MoD said.
An Army spokesman added: "We can confirm that all Army cadets caught in today's inclement weather on the Mourne Mountains are safe and accounted for."
The Mournes are a range south of Belfast which is extremely popular with walkers but like all mountains the conditions can be unpredictable.
The group included children aged from 12-17.
Emergency services were called to the scenic Annalong Valley at around midday.
A Mourne Mountain Rescue spokesman said it was not a major incident but weather had caught them out.
He added: "It is nothing out of the ordinary.
"Everything is under control and within normal team procedure."
Northern Ireland Ambulance Service paramedics provided medical support.
Newcastle, Bangor and Kilkeel Coastguard Rescue Teams, and the UK Coastguard search and rescue helicopters based at Caernarfon and Prestwick, were on scene.
Also attending were the Irish Coastguard Rescue 116 helicopter, Mourne Mountain Rescue Team, Police Service of Northern Ireland (PSNI) and ambulance service.
An MoD spokesman said: "We are exceptionally grateful for their assistance."
Earlier: Over half of the young army cadets have been rescued after they got into difficulty in the Mourne Mountains.
Up to 16 people are being treated for hypothermia.
A major rescue operation is underway to take the British army cadets to safety.
Up to 70 young people got into difficulty while camping in the Carrick Hill area.
46 of the group - mainly aged between 12 and 17 - have been brought down by 4-by-4 so far.
17 others remain on the mountain.
Some are said to suffering from the effects of hypothermia and some have lower leg injuries.
An army spokesperson said that all of the cadets are safe and accounted for.
Liam Colquhoun from the Coastguard said bad weather is hampering efforts to bring the young people to safety.
"Unfortunately, we've had to stand two of the aircrafts down due to the fog so they're down to about 20 metres now," he said.
Earlier:Up to 16 people are being treated for the effects of hypothermia after getting into difficulties in the Mourne Mountains in Co Down.
A major medical emergency was declared just before lunchtime after a group of around 70 army cadets got caught up in torrential rain.
It is understood the group had been camping close to the Carrick Hill area.
The casualties are being taken to Annalong Community Centre to be assessed.
Local MLA Colin McGrath has been watching the rescue unfold.
He described the weather as "atrocious" today and said that it is understandable that the youngsters got into trouble.
He also said that there have been more than a dozen ambulances passing through Newcastle in the last hour to attend the scene.
Earlier: Rescue teams are currently assisting with a large scale incident involving up to 70 Army Cadets in the Mourne Mountains in Co Down.
According to the UK coastguard, they receiving a call just before 12pm today requesting assistance after receiving several reports that a large number of people were in difficulty.
It has been reported that the group were caught out in inclement weather while walking.
They said that initial reports suggest that all members of the group are accounted for, however four people may be suffering from exposure.
A number of people are said to have sustained lower leg injuries.
Newcastle, Bangor and Kilkeel Coastguard Rescue Teams, and the UK Coastguard search and rescue helicopters based at Caernarfon and Prestwick are on the scene.
The Irish Coastguard Rescue 116 helicopter, Mourne Mountain Rescue Team, PSNI and NI Ambulance Service are also on scene.
The three helicopters are currently situated at Donard Park due to poor weather conditions and will support casualty evacuation as further information comes in.
More to follow…
Earlier: Helicopter, coastguard and medical response teams have been sent to the aid of 40 army cadets after they got into difficulty in the Mourne mountains.
The Ministry of Defence told the BBC that the cadets, aged between 12 and 17, had been camping when they got into difficulties
It has been reported that medical staff are treating several children at the scene.
Local politician Colin McGrath tweeted: "Major emergency incident in mournes with helicopter, coastguard, medical and ambulance responding. Please God all will be ok."
Earlier: A major rescue operation is underway in the Mourne Mountains in Co Down.
There are reports that are 70 people stranded in the area.
Ambulances are attending the scene and it is reported helicopters are on their way.
Some people have been treated at the scene.