COPENHAGEN -- Swedish authorities say a powerful explosion outside a police station in southern Sweden has caused significant damage to the building. There have been no injuries and nobody has been arrested.

Police haven't said what caused Wednesday's pre-dawn blast at the police station in Helsingborg, but the country's top police official, Dan Eliasson, called it "an attack against society." The explosion caused considerable damage to the police station's entrance and shattered dozens of windows in nearby buildings.

A police officer guards outside a cordoned area surrounding the police station in Helsingborg, Sweden, after a powerful explosion at the main entrance, October 18, 2017. REUTERS

No one has claimed responsibility for the blast about 30 miles north of Malmo, Sweden's third largest city.

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Suburban feuds between criminal gangs fighting over territory have taken place in major Swedish cities in recent years. The explosion wasn't immediately being investigated as terrorism.