More than two dozen people are recovering after they became ill from alcohol or drug use while attending a huge concert in Toronto on Saturday night.

Paramedics said 29 people were suffering from “various degrees of illness” and had to be taken to hospital from Rogers Centre, where Swedish DJ Avicii was performing a sold-out show in front of tens of thousands of people.

EMS commander Peter Rotolo said most of the patients drank too much alcohol and at least one person was treated for drug use.

One person was arrested by police.

Five people were in serious condition but everyone is expected to make a full recovery, paramedics told CP24.

Rotolo said those who became sick began drinking before the concert and some were transported to hospital before the electronic dance musician took to the stage.

He said city paramedics were not on standby at the concert but they had to be called in when private medical professionals became "overwhelmed" by the number of patients.

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