CCTV shows the fire at Holy Family in Ballymagroarty was started by youths, the fire service says.Read more
Northern Ireland Fire and Rescue Service
More than 50 firefighters battled the blaze on Sunday in the foothills of the Mourne Mountains.
Residents of Tullybrannigan Road were also among those forced to leave their homes.
Residents of the nearby Bonny's Caravan Park have been evacuated.