The man, who denies having anything to do with the blaze, was arrested on Wednesday evening in connection with other crimes, including drug offences. Information emerged during questioning that caused prosecutors to decide to keep him in custody in connection with the fire at the Scandic Grand Central hotel.
Prosecutor Mikael Hammarstrand told Swedish Radio that the evidence against the man is currently patchy, but that interesting information had emerged. Police are also questioning hotel guests and other witnesses.
The fire completely destroyed older parts of the hotel and the CH nightclub, which was on the ground floor of the building.
Fire investigators have so far been unable to get into the hotel, as the building is unsafe.
“The risk of collapse is too great to allow them to go inside and start their investigation,” said Torbjörn Säfström, who is leading the police inquiry into the blaze.