More than 20 people have been taken to hospital with carbon monoxide poisoning after attending a rave in an underground bunker in the Norwegian capital, Oslo.
Police say the party was discovered by accident when a patrol came across a group of young people acting confused early on Sunday.
Several others then came out of a bunker and called for an ambulance.
Authorities believe the poisoning was caused by portable generators.
Two of the 25 victims are believed to be police officers who treated the revelers.
“Fortunately, they’re all improving. We can say they are out of danger, ”Chief Medical Officer Fridtjof Heyerdahl of the University Hospital in Oslo told the newspaper.
Around 200 people were said to have attended the rave, according to the Oslo police.
Police also called on other participants to see a doctor if they began to experience nausea, headaches or dizziness.
One person who left before the police arrived told NRK that he left the rave to get fresh air on numerous occasions due to the poor air quality inside.
Oslo Police said they were investigating why information about the rave was not taken into account.