Half of the 17th-century Borsen building was burned and its 54-metre (180-foot) spire tumbled to the ground in the fire that broke out on Tuesday morning, in scenes that shocked Denmark.

No one was injured in the fire, and many of the valuable paintings hung inside were rescued but enormous damage has been done to one of the Danish capital’s most loved landmarks. 

Emergency services announced the blaze was under control on Tuesday but it continued to burn in the part of the building, which had been undergoing renovation.

Close to the Christiansborg parliament and seat of government, the old stock exchange was commissioned by King Christian IV and built between 1619 and 1640, and continued to serve as the site of the city’s stock exchange until 1974.

On Wednesday morning, firefighters were still tackling flames in the damaged part of the building, “where only the exterior walls remain”, they wrote on X. 

They added they were working to secure the stability of the walls and monitoring undamaged areas. Firefighters predicted they would be battling the flames for another 24 hours.

The walls will be stabilised with more than 40 temporary buttresses, which will be placed against the outer walls of the building to prevent them from collapsing. The first of the buttresses have already arrived and been installed. 

“They should prevent the outer walls, which remain in the burned-out part, from collapsing and posing a danger to everyone who moves in the area and our crew,” said Frank Trier Mikkelsen, operations manager in Copenhagen’s emergency department. “At the same time, it is also an attempt to preserve what remains of the historic masonry, which can possibly be used in connection with the reconstruction.” 

“When all the buttresses have been set up, we will make a reassessment in collaboration with engineers who calculate the stability. Then it will be assessed what the risk is in the area and how much can be opened up,” he added. 

The cause of the fire is unknown and investigators are yet to access the site, one of the capital’s oldest and best-known landmarks that holds a vast art collection and houses the Danish Chamber of Commerce.

When the fire has been completely extinguished, Copenhagen police enter the building to start technical investigations the cause of the fire.

They have already started interviewing some of the employees who were in or near at the building at the time the fire broke out on Tuesday morning.

“The investigation was already started shortly after the outbreak of the fire and we have already carried out interviews, ensured surveillance and carried out a long series of investigative steps,” Brian Belling, head of the city police’s Department for Crimes Dangerous to Person, said in a press release. 

“But of course there is still a lot to be done, especially since at this stage we have not yet had the opportunity to examine the Stock Exchange itself and carry out technical investigations.” 

In the press release, the police said that it could take “several months” before the cause of the fire would be determined. 

“It can take a long time to uncover the cause of a fire in such investigations. Therefore, we must ask for a little patience from the public while we carry out our work,” Belling said.