A school near Gothenburg in western Sweden was evacuated Monday after a bomb threat.

The principal at the Alle school in Floda outside of Gothenburg received a phone call around lunchtime Monday warning that "an explosive item" had been placed somewhere in the school.

"We have, together with the principal, decided to evacuate the pupils and teachers... Someone apparently stored something explosive inside the school," police spokesman Hans Lippens told news agency TT.

Lippens said police are taking the threat seriously and that evacuating the school's roughly 500 pupils and 70 teachers was a first step.

"Things will have to stand still for a while before we determine if we need to take any further steps and search the facilities," said Lippens.

The pupils realized there was an emergency situation when the fire alarm went off. They were told to gather at a sports field near the school building where they were counted. They were then given the rest of the day off.