A fire raged through one of Copenhagen’s oldest buildings on Tuesday, causing the collapse of the iconic spire from the 17th-century Old Stock Exchange as passersby rushed to help emergency services save priceless paintings and other valuables.

Danish culture minister Jakob Engel-Schmidt said it was “touching” to see how many people lent their hand “to save art treasures and iconic images from the burning building.” One man jumped off his bicycle on his way to work to help in the effort.

Brian Mikkelsen, chief of the Danish Chamber of Commerce, which is headquartered in the Old Stock Exchange, and his staff were seen scrolling through a binder with photos of paintings to be saved. They were carried to the nearby parliament and Danish National Archives, around the corner from the burning building.

“We have been able to rescue a lot,” a visibly moved Mikkelsen told reporters. “It is a national disaster.”

He also took part in saving paintings and other valuables from the flames and said they had to use tools including a crowbar to remove them.

The fire began on Tuesday morning in the copper roof of the Old Stock Exchange, or Boersen, spread to much of the building and the roof, parts of which also collapsed, and destroyed the building’s interior, said firefighters spokesman Jakob Vedsted Andersen.

“The fire is still not under control,” Vedsted Andersen said, adding that half the building was destroyed and collapsed. He said that there was no risk of the blaze spreading to other buildings. Firefighters said they expect to be at the scene for the next 24 hours.

Tommy Laursen of the Copenhagen police said it was too early to say what caused the fire and that they would be able to enter the building in “a few days”.

Firefighters who reportedly pumped water from the nearby canal were seen spraying water through the doorway of the Old Stock Exchange’s gilded hall that is used for gala dinners, conferences, parties and other events and where many of the paintings hung.

The building, which is situated next to the Christiansborg Palace where the parliament sits, is a popular tourist attraction and has been photographed millions of times. Its distinctive spire, in the shape of the tails of four dragons, twined together, and reached a height of 56 metres.

Huge billows of smoke rose over downtown Copenhagen and people were seen rushing inside the building to save paintings. The plume could be seen from southern Sweden, which is separated by a narrow waterway.

Ambulances were at the scene but there were no reports of casualties. A spokesman for the company working on renovating the building said the carpenters who worked on the roof had all come out. Up to 90 members of an army unit were also deployed from a nearby base to cordon off the area and “secure valuables”.