Five people were found unconscious in a caravan in eastern Norway, near the border with Sweden.
Four of the affected individuals have been taken to hospitals in Oslo by helicopter.
Their condition was initially described as critical and life-threatening, but by Tuesday afternoon, the hospital announced that the situation had improved slightly.
The patients are getting better, but at the same time, it's difficult to say whether the incident will have consequences for their health in the long term, says Katharina Lende, head of the hospital's emergency department, to Dagbladet.
The condition of the fifth person has not been disclosed.
The authorities were alerted at 1 am on Tuesday. The caravan was located in Rendalen, approximately five miles from the border with Sweden, near Idre in northern Dalarna.
There is suspicion of gas or carbon monoxide poisoning, said Mats Westby Aamodt at the Innlandet police earlier in the day.
The individuals involved are not Swedish citizens, according to the Norwegian police for TT.
