An explosion ripped through a Norwegian dairy plant building in the country's southeast on Monday, killing at least one person and wounding three others, a Norwegian broadcaster reported. Rescuers also sought five people believed to be missing.

Police spokesman Jon Erik Nygaard told broadcaster NRK that the blast in Fredrikstad seems to be due to a "large gas explosion."

Hilde Floekstad, a manager at the Mills plant, said the afternoon blast occurred in connection with service being performed on a gas tank.

"When the gas tank was empty, something happened that led to the explosion," she said.

Police have cordoned off the area and footage from the scene showed significant damage to parts of the plant as well as surrounding buildings.

According to news agency NTB, 20 to 25 people were working in the factory at the time of the explosion.

Rescue services spokesman Ola Vaage told NTB that police were using dogs to search for five people who could be missing.