MILAN (AP) -- Italian authorities are investigating an explosion outside the Bologna station of the Carabinieri national police that damaged the building overnight, but caused no injuries.
News agency ANSA reported that video surveillance showed three people dressed in dark clothing with their faces covered and wearing gloves igniting two gas canisters by the police station's entrance early Sunday,
The blast ripped through the station's glass door and shattered windows.
Italian Environment Minister Gianluca Galletti visited the scene, calling the attack, "cowardly," while politicians across the spectrum decried the violence.
Premier Matteo Renzi traveled to Bologna later Sunday to campaign for an upcoming constitutional referendum. Bologna's mayor told Sky TG24 that he believed the blast was unrelated.