A powerful explosion has been reported at a school in the Swedish town of Karlstad, according to local media say.

After the explosion a fire broke out and emergency services rushed to the site, but there have been no reports of casualties so far.

“We are on site now and are trying to ascertain what has exploded,” Ola Akesson of Karlstad’s emergency services told the Expressen newspaper adding that the explosion was so powerful that it was heard in other parts of the city, too.

“There was a very loud bang. We thought it was a bomb,” one of the teachers, told the NWT newspaper, while public broadcaster SVT reported that the source of the blast might have been in the school’s gym.

The building was immediately evacuated, while students are socked.