Emergency services in Belfast were last night dealing with what they term "a major incident" at the Odyssey Arena, the city's largest entertainment venue.
The Ambulance Service and the Ulster Hospital in Dundonald, with other Belfast hospitals in support, treated dozens of young people, understood to be mostly teenagers, for the effects of alcohol and drugs.
Some were in varying stages of unconsciousness.
One early and unofficial report suggested that up to 20 had been taken to hospitals across the city, while more than 50 were being treated at the venue by paramedics who arrived in a fleet of emergency vehicles and ambulances.
The “major incident” was declared, it is understood, because of the scale of the response by emergency services and not because of the numbers affected at the incident.
According to UTV, a spokesperson for the local health trust said it was aware of an incident involving a bus at the Odyssey, where internationally renowned DJ Hardwell was scheduled to perform.
It is thought the bulk of those affected were linked to a bus arriving at the venue and that many of them were already under the effects of drugs and/or alcohol.
The Dutch DJ is a huge hit with teenagers and the gig was open to ticket holders from 6.30pm. Only those over 16 were allowed in. More than 7,000 were in attendance at the venue.
News spread
Many worried parents began arriving at the Odyssey in cars as news of the incident spread quickly.
The Ambulance Service told BBC Northern Ireland the problem in the majority of cases was intoxication.
A spokesman said many of those were already intoxicated when they arrived at the venue.
John McPoland said: “We believe the majority arrived suffering from too much alcohol. We declared a major incident because of the number of resources we had to deploy to the scene.”
Adrian Doyle, a spokesman for the Odyssey Arena, said: “It is our understanding that a number of patrons arriving to attend a concert by Dutch DJ act Hardwell have required medical attention, having already been intoxicated on their arrival at the complex.
“These patrons were not granted entry to the Odyssey Arena, and were treated by the Ambulance Service outside.”
Belfast city councillor Niall Ó Donghaille of Sinn Féin, who represents the nearby Short Strand area, said he believed that about 20 young people had been taken to the Ulster hospital at Dundonald about 5km away from the venue. Other Belfast hospitals, the Mater and the Royal Victoria, were acting in support.
Mr Ó Donghaille later tweeted that the emergency services had the situation under control.
East Belfast councillor and former lord mayor Gavin Robinson of the DUP said he believed none of those affected had life-threatening conditions.