Oslo cave rave leaves dozens in hospital with carbon monoxide poisoning

Diesel generators at packed party led to dangerously low oxygen level, fire brigade said

Twenty five people in total were treated for carbon monoxide poisoning after cave rave (Getty)

Dozens of ravers were rushed to hospital with carbon monoxide poisoning after a party in a packed cave in Oslo, police have said.

Up to 200 people had gathered at a cave in the Norwegian capital for a birthday party complete with sound system, not realising the danger of using diesel generators in so tight a space, Oslo Police said.

A total of 25 people were hospitalised as a result of exposure to carbon monoxide, seven of whom were unconscious on arrival, Oslo's Dagsavisen newspaper reported. Five people were critically injured, police said.

Two of the patients were police officers who were exposed to the deadly gas while helping to evacuate partygoers.

A sound system had been packed into the cave and was powered by portable diesel generators, which combined with the ravers was enough to plunge the oxygen level to around 16 per cent, far below what is safe, Ronny Andersen of the Oslo Fire Service told local reporters.

The fire brigade worked through the night to drive fresh air into the cave, pumping oxygen through a tube in the 1x1m entrance, Mr Andersen told Norway's VG newspaper.

"It was a rave in honour of someone's birthday, attendees we have spoken to have been between 20 and 30 years old," said Arve Rotterud from Oslo Police.

Mr Rotterud said police were alerted to the incident when a partygoer waved down a patrol car at the side of the road in Oslo's central St Hanshaugen district.

“Carbon monoxide poisoning should be taken seriously, and several there were under the influence of drugs when they left, it could have been a lot worse,” Mr Rotterud said.

"We encourage anyone who was at the party and has experienced discomfort to contact the health service," Oslo Police said in a statement.