The blast resulted in the evacuation of the Blue Moon Bar in Västerås on Sunday night, although no one was injured in the mysterious blast.
Bomb tecnicians have claimed that the the incident “was no accident”.
Nearly 700 people were in the nightclub at the time of the explosion, which occurred on the terrace of the club just after midnight, and also resulted in the evacuation of a small hotel nearby.
According to one patron of the club, there was an enormous sense of confusion inside as the music was cut and the guests were told to leave.
“We were on the dance floor and saw one of the security guards rushing to the DJ, and the music was quickly turned off,” one witness told The Local.
“Everyone was puzzled – a voice came over the speakers telling us we had to leave – we weren’t even allowed to get our jackets until the next day. None of us heard the explosion as the music was so loud inside.”
The witness explained how the patrons were alerted to the fact that a bomb had gone off on the outdoor terrace, and that no one was injured.
“No one seemed panicked though. By the time we knew what had happened on the terrace, there was no longer any unrest. As far as we heard, only some glass got smashed from the blast. Many people even went on to another club,” the witness told The Local.
The patrons were left standing outside with their drinks in hand, and many were left without their keys and phones which were inside their jackets in the closet, according to the witness.
Police are now investigating the incident, yet have identified no suspects.
“Bomb technicians have been on the scene and we still have our own technicians working there too,” said Åsa Hedin of the Västmanland police to TT.
“We’re getting many tipoffs from the public and this is something that we hope continues.”
Police also interviewed the long line of people who came to collect their jackets on Sunday.
The event has been labelled as public devastation by police, who as of Sunday night still had no suspects in the case.