Others detained in connection with the investigation into the bomb threat who were released on Saturday remain of interest.

Ulf Edberg, a press spokesperson in the county of Västra Götaland, explained that the police readiness extends to among other things an special unit to be called in if needed.

“There are however additional police officers deployed in central Gothenburg,” he said without going in to how many and where in the centre of the city they are stationed.

Gothenburg police have also desisted from releasing concrete details over those who remain in custody, those who were released, and the bomb threat itself. Broadcaster TV 4 has reported that three men were detained in the district of Angered.

Edberg confirmed that the cautious approach has been decided upon “with respect to the investigation”.

Police were neither willing to detail any possible motives behind the threat and where in Gothenburg the bomb was said to be located.

The raised threat level was in place during the whole of Saturday, with nothing to indicate whether it remained in place during Sunday, with Edberg unwilling to comment.