Police in the southern Norwegian city of Fredrikstad said that one person was killed in the powerful gas explosion which blew up a building in the Mills factory on Monday afternoon.

At the scene of the explosion, Terje Marstad, police superintendent for Fredrikstad, told Xinhua that three persons were injured and that no one was missing. Earlier reports said that there were five persons missing.

A gas tanker was engaged in maintenance service at the Mills factory, which mainly produces butter and edible when the explosion occurred at 16:18 local time (1418 GMT).

The deceased was the 62-year Vigbjoen Dan Larsen, who was together with others performing the maintenance.

Glass panels were blown out of the windows of the nearby buildings and twisted metal parts and debris fell and scattered on the ground.

Police and rescuers were working on the site and two air ambulances were dispatched from Loerenskog and a rescue helicopter from Oslo.

The police said they were trying to establish what had caused the accident.

The Norwegian broadcasting company NRK reported that there was a gas leakage during the maintenance.