After days of intense flooding in the area, a dam on a Norwegian river partially collapsed on Wednesday, sending water flowing through a large hole in the structure, according to TV photos.

The Braskereidfoss hydroelectric dam on Norway’s largest river, the Glomma, had been unable to open its hatches when its control room flooded.

Water appeared to flow through the dam in an orderly manner following the breach, utility Hafslund said in a statement.

There were no immediate signs of major downstream flooding, a police spokesperson said.

Police earlier considered blowing one of the hatches of the 45-year-old dam to help relieve the situation, but decided against doing so as the explosion would have been difficult to control.

Norway has evacuated thousands of people as rivers swelled to their highest levels in at least 50 years, and homes and businesses were submerged or swept away by landslides.

Main roads were closed and train services suspended across wide parts of southern Norway as rivers breached their banks, and authorities warned of more flooding to come in the days ahead as the water moves towards lower-lying coastal regions.

A railway bridge collapsed on the line connecting Oslo to Trondheim, Norway’s third-largest city, but there was no risk to people as trains had already been suspended since Monday.

Innlandet county, one of Norway’s worst-hit areas, said many people were isolated by the floods and that first responders may not be able to reach those in need.

“We’re in an emergency situation of national dimensions,” Innlandet Mayor Aud Hove said in a statement.

The government on Wednesday decided to mobilise more helicopters to take part in the evacuation, the ministry of justice and public security told broadcaster TV2.

Strong winds, intense rain and landslides hit different parts of the Nordic region in recent days, knocking out power lines in Finland, flooding villages in Norway and Sweden and bringing public transport to a standstill in hard-hit areas.

On Monday, a Swedish train derailed when a railway embankment was washed away by floods, injuring three people.

Authorities in Norway and Sweden maintained red alerts, their most severe flood warnings, for several regions on Wednesday.