According to the Yle News outlet, there is no indication that the blast was deliberate. The local police and rescue services arrived at the site, while journalists have been denied access to the building.
The theater's technical director, Atti Rehtijarvi, told the news outlet that there were about 100 people in the building at the time of explosion, as regular maintenance was being carried out in there as part of preparations for the next season.
The police have launched an investigation into the incident, the media stated.