The Öresund bridge links Malmö in Sweden and Copenhagen. Photo: Johan Nilsson/TT
Drivers raised the alarm at around 7am after noticing a person walking inside the four kilometre long tunnel at the start of the bridge which connects Copenhagen with the Swedish city of Malmö.
"This person was actually walking on the motorway and people saw it and called the police," Sanna Holmqvist, Head of Public Relations for the bridge, told The Local.
She said that security staff used their network of some 400 cameras to trace the exact location of the person, who was inside the section of the tunnel where drivers are usually allowed to reach 90 kilometres per hour.
"We shut one of the lanes and we took down the speed limit in the other lane to 50 kilometres an hour and by then the police were already on the way," said Holmqvist, adding that the whole incident was over in around 15 minutes.
One witness posted in a Facebook commuter group that they feared there had been a bomb at Copenhagen's Kastrup airport, which is linked to the bridge by train, Swedish newspaper Sydsvenskan reported.
Another driver said they had needed to "slam on the brakes in the tunnel at the request of the police because someone is here," said the paper.
Holmqvist would not comment on speculation that the person found was a refugee attempting to walk over the bridge to Sweden, adding that it was now a matter for Danish police.
However she noted that efforts to make the journey on foot were unusual.
"It does happen now and then because it's an open motorway (...) we don't really have statistics."
The extra checks have added an additional 40 minutes to the daily journeys of thousands of people commuting between the two countries.