It happened after a report of a commotion from an apartment.

There were messages from several people, says operations manager Ron Heckelstrand. It was a loud explosion that many heard, and it also shattered some glass panels in the street.

The police were able to control four people who were in the apartment. One of them suffered facial injuries that did not appear to be serious.

VG's freelance photographer spoke to incident commander Erik Hestvik at the scene just after 03:00 and said it was an “explosive fire”.

-We took care of four people who were present. They were taken to Olival Hospital, where two of them suffered moderate burns.

There was no spread to other apartments.

Police reported earlier last night that it appeared a light bulb had exploded in the bathroom, but police had reached no conclusion.

We are still at the scene and conducting investigations. Heckelstrand says at 02.50.

Operations Commander Histvik says police are working in the apartment and are questioning those involved at the hospital.

He added that he had no information that anything criminal had occurred, but he said they were conducting investigations to uncover what happened.

– There are investigations of a legitimate nature, after which we will talk to those involved.