Updated

A gas explosion ripped through a building of a Norwegian dairy plant in the country's southeast on Monday, killing at least one person and wounding three others, police said. Local media reported that rescuers also sought five people believed to be missing.

According to news agency NTB, 20 to 25 people were working in the factory at the time of the explosion. Police cordoned off the area and footage from the scene showed significant damage to parts of the plant as well as surrounding buildings.

"One person is confirmed dead and three people have been injured," police in Fredrikstad said in an e-mailed statement.

The statement said a "large gas explosion" was involved and added that police had requested aid from Oslo, which is sending a bomb squad to the scene.

Hilde Floekstad, a manager at the Mills plant, told broadcaster NRK that service was being performed on a gas tank.

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

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