There are no reports of serious personal injuries, according to the police.
It was a really powerful explosion, said Magnus Jansson Klarin, police spokesperson after the incident.
What detonated at the gate has not been determined yet, but it is believed to be some kind of explosive charge.
At 07:30 on Thursday morning, no suspected perpetrator had been arrested yet.
But it is our stated ambition to apprehend one or more individuals in the case, says police spokesperson Pelle Vannstad.
Several apartments are said to have had their windows destroyed in the explosion. The National Bomb Squad has been there and investigated the site, which is located in the so-called Industrial City in the Kungsängen district.
The police received calls about the blast minutes after midnight, from many Uppsala residents, including people who live quite far from the site.
The explosion is being investigated as general endangerment.
