The cause of the incident remains unclear.
The Femern Link Contractors (FLC) consortium, which is building the tunnel beneath the Fehmarn Belt strait, has been hit by what the investor, Sund & Baelt, described as a "cyber incident."
Danish newspaper Folketidende reported that workers’ identification cards had stopped functioning and that vessels, cranes, and offshore platforms used in the construction work had been immobilised.
Jens Villemoes, a representative of Sund & Baelt, said the company was in talks with FLC about the situation.
It remains unclear who was behind the incident and how long its effects will last.
Henning Mortensen, chairman of Denmark’s Council for Digital Security, told Danish broadcaster TV 2 that the incident could be linked to hybrid warfare.
In late September, Danish Defence Minister Jeppe Brus and Thomas Ahrenkiel, head of Denmark’s military intelligence service, warned of the risk of serious hybrid attacks and other incidents originating from Russia.
Following those warnings, Denmark’s public security agency raised the cyber threat level from medium to high.
Cybersecurity expert Jacob Herbst said that advances in artificial intelligence were making it easier to carry out large-scale cyberattacks with limited resources.
"The pace of change is so rapid that many organisations cannot keep up with closing security vulnerabilities," Herbst said.
FLC employs around 2,800 people and brings together companies from Denmark, Germany, France, Belgium and the Netherlands. A large proportion of the construction workforce are Polish workers.
The Fehmarn Belt tunnel is designed to provide an 18-kilometre road and rail connection between Denmark and Germany.
It will consist of 89 prefabricated concrete sections submerged beneath the sea.
The sections, each measuring 217 metres, are being produced at a temporary factory in the Danish port of Rødby.
They are then transported by vessels and platforms and joined together with the help of digital software that enables precise positioning.
The project is estimated to cost around EUR 7 billion.
In autumn 2025, the Danish consortium behind the project said that the original opening date of 2029 was unlikely to be met because of delays.
(pg/gs)
Source: PAP