Three days after a fire which ravaged Copenhagen's historic former stock exchange broke out, emergency services said on Friday that the situation was "unstable" due to equipment issues and a strong breeze.

In the morning, during work to dismantle the scaffolding surrounding the building, a crane's cutters came loose for as of yet unknown reasons.

It is currently wedged between the scaffolding -- put up for the renovation of the historic building that was ongoing -- and what remains of the walls.

"It is affecting our efforts", Tim Ole Simonsen, leader of the operation at the rescue services, told a press conference.

Coupled with the wind picking up, the incident, which has temporarily halted work on dismantling the scaffolding, has made the situation "unstable".

"The wind is blowing harder and harder, and there are tarps over the scaffolding that can catch the wind," Simonsen said.

He added that this increases the risks, in particular of further collapse of the burnt-out facade which started collapsing late Thursday afternoon.

Located close to the Christiansborg parliament and seat of government, the Borsen building was commissioned by King Christian IV and built between 1619 and 1640. It was the stock exchange until the 1970s.

The fire began Tuesday morning under the copper roof of the building, which was undergoing renovations ahead of its 400th anniversary.

The cause of the blaze was unknown and Copenhagen police said Wednesday that a major investigation had been launched.