Books of Condolence have been opened across County Tyrone in memory of three young people who died in a crowd surge on Sunday night.
CCTV footage is being examined after teenagers were caught in a crush outside a disco in Cookstown.
The PSNI has asked parents to talk to their children about what has happened.
President Michael D Higgins says it was a 'terrible loss of life on St Patrick's Day' and has offered his condolences to the friends and families of the victims.
Catherine McHugh is the principal of the college where one of the teens who was killed, Lauren Bullock, attended.
She says the pupils have taken part in a prayer service to remember her.
