ARSONISTS are responsible for the blaze which burned Blackwood Youth Centre to the ground.
Flames engulfed the centre in the early hours of Sunday morning, leaving just a buckled shell after fire crews battled with the blaze for more than five hours.
Yesterday, a fire service spokesman confirmed the fire is being treated as suspicious.
The Caerphilly council-owned building was used by hundreds of youngsters every week for youth groups, exams and community projects.
The council said it could not confirm the cost of the damage as it was being dealt with by insurers.
The spokesman added: "We are obviously very saddened to see the destruction of this well used community facility and we now await the outcome of the investigation into the cause of the blaze.
"We are working hard at the moment to find alternative provision for the many groups and organisations that use the centre and we are hopeful that new venues can be identified quickly so that disruption is kept to a minimum."
The fire was started at the centre in Woodbine Road at around 1.50am and firefighters worked through the night to bring the fire under control.
Residents living next to the centre were warned they could be evacuated if the wind changed direction, causing sparks to spread, but this was not needed.
Around 80 youngsters regularly went to an evening youth group at the centre, which also hosted a young mums' project and a parent and toddler group.
It had a computer room, large hall, kitchen, television room, snooker table and changing rooms.
No-one was inured in the fire.
Gwent Police is appealing for anyone with information about the fire to call 101 or Crimestoppers on 0800 555 111.
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