Police have launched an investigation into a mass underage drinking binge that saw more than 100 young concert-goers treated by medics in Belfast.
Eighteen people were hospitalised in the wake of last night's incident in and around the Odyssey Arena, where Dutch DJ Hardwell was playing to a crowd of 10,000.
Police said around 300 young people were refused entry to the premises - some of whom were drunk and others too young to gain entry to the 16-and-over gig.
Around 40 required care from medics, ambulance crews and charity volunteers who set up an ad hoc treatment area outside.
Inside the Odyssey, 68 concert goers needed medical assistance.
There were reports of a number of fights breaking out and widespread drug taking.
A major incident was declared by the Northern Ireland Ambulance Service and in two of the city's hospitals, where extra staff were called in to help.
None of those admitted to hospital were deemed to be in a serious condition.
Police are investigating how so many children were able to access alcohol. Some drugs were also recovered by police outside the venue.
Three people were arrested during the course of the night - a man aged 21 was detained for disorderly behaviour, another aged 18 was arrested for assault and resisting police arrest, and a 16-year-old woman was arrested for assault and resisting arrest. They remained in custody at a city centre police station today.
Police Service of Northern Ireland (PSNI) chief inspector Mark McEwan said: "Police are meeting with Odyssey Arena to review the incident and will be conducting an investigation. CCTV will form part of that process."
The senior officer added: "Police would encourage parents that may be considering allowing their child to attend an event where there is an age restriction to ensure that the child is the appropriate age."
Odyssey general manager Adrian Doyle said, as with any concert, the safety of patrons was an absolute priority at all times and the event control team was confident that it had sufficient staff on site to maintain a safe and enjoyable concert.
He said anyone who turned up to the event visibly drunk was not allowed in.
The Stormont Assembly has been urged to investigate how young children in Northern Ireland are able to get their hands on drink.
Colin Neill, chief executive of Pubs of Ulster which represents local bar owners, said: "Somewhere someone gave these kids alcohol and I think it's time to call an end to it.
"I think we need more than a police investigation, I think the Assembly needs to get involved."
A spokesman for the Northern Ireland Ambulance Service said: "We believe the majority arrived suffering from too much alcohol."
He added a number of people were unconscious at the scene.
Dr Tony Stevens, medical director at the Belfast Health Trust, paid tribute to staff in the Royal Victoria and Mater hospitals that were involved in the response.
"We handled it very well," he said. "I am very grateful to the large numbers of specialist staff that came in, and indeed all the staff - we had everybody from telephone operators to portering staff who were helping."
Dr Stevens told Radio Ulster: "The busiest team were the ones answering the telephones because parents were unable to contact their children at the scene."
Hardwell was named the world's number one DJ in the 2013 DJ Mag top 100 DJs poll.
His hits include Spaceman, Three Triangles (Losing My Religion) and Apollo.
Last month dozens of fans camped overnight or queued for hours on a Belfast street in pouring rain for a ticket to his show.
Mr Doyle later insisted the number of adverse incidents inside the arena were not on an unusual scale.
"Incident levels inside the Odyssey Arena before, during and after the Hardwell concert were at normal levels for an event of this size and nature and were managed effectively at all times by staff," he said.
He said thorough pre-planning had taken place with the PSNI and Belfast City Council.
"Decisions were taken at this meeting, to ensure safety, caution and good management of the event and a detailed management plan was agreed and put in place," he added.
"Both the PSNI and Community Enforcement Teams from Belfast City Council were on the ground at the event confiscating alcohol that was in the possession of patrons as they arrived at the Odyssey.
"In anticipation of any patrons being turned away at the door for any reason, the support services of the SOS Bus were also deployed.
"High levels of staff were employed to manage queues at the door. Searches were carried out on the door by a team of Security Industry Authority (SIA) accredited personnel, with two PSNI sniffer dog teams also deployed. Large numbers of patrol and response staff were on the concourses and in the main hall throughout the evening and supervisers checked toilet facilities on an ongoing basis.
"Stringent ID checks were in place under the 'Think 21' guidelines for any patrons wishing to purchase alcohol within the Odyssey Arena, with patrons required to produce a valid passport or driving licence as proof of ID. Purchase of alcohol was limited to two drinks per ID, and all alcohol sales were stopped at 9pm."