UPDATE: 18 of the 24 missing children have been found.
According to reports, a rescue helicopter has landed and the crew is with the children.
Their condition remains unknown at this time.
Western Mountain Rescue Team have said that they think they know where the there six children are, but they cannot be sure.
According to multiple reports, the alarm was raised at 1pm.
Since then, three mountain rescue teams and the police have been searching tirelessly for the missing children.
A Dyfed-Powys Police spokesman said: "Concern was expressed for their welfare due to the inclement weather.
"Mountain Rescue Team are leading the search activity and the UK Coastguard helicopter is also assisting."
Mark Moran, from Central Beacons Mountain Rescue, added that the search party believes they have located the youngsters.
However the children are lost in the clouds, and rescue helicopters are unable to land.
A spokesman explained: “A recent update from incident control has advised that the MCGA rescue helicopter from St Athan has spotted the group and is unable to land.”
Two of the school children - who are on the beacons as part of their Duke of Edinburgh Award - are believed to be suffering the effects of hypothermia.
The rescue team is in intermittent phone contact with the children, and it has been confirmed that they do not have an adult with them.
Speaking to The Mirror, a local pub owner explained that his car park is being used as a rescue centre - and that teams are preparing for the youngsters, all of whom are in their mid-teens, to be brought down.
He said: “The car park is full of about 10 or more emergency vehicles.
“They are on their way down.
“A helicopter passed overhead about five or six minutes ago.
“We’ve got everything warm here.”
We will bring you more on this story as it develops.