Gas canisters detonated outside Italian police station

An Italian Carabinieri paramilitary police officer stands outside a Carabinieri station damaged by an explosion, caused by two canisters of gasoline ignited by a fuse in Bologna, Italy, Sunday Nov. 27, 2016. Italian authorities are investigating the overnight explosion that damaged the building but caused no injuries. (Giorgio Benevenuti/ANSA via AP) (The Associated Press)

Italian Carabinieri paramilitary police officers stand outside a Carabinieri station damaged by an explosion, caused by two canisters of gasoline ignited by a fuse in Bologna, Italy, Sunday Nov. 27, 2016. Italian authorities are investigating the overnight explosion that damaged the building but caused no injuries. (Giorgio Benevenuti/ANSA via AP) (The Associated Press)

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 a fuse ignited two canisters of gasoline by the entrance of the Carabinieri station early Sunday. The blast ripped through the station's glass door and shattered windows.

Italian Environment Minister Gianluca Galletti visited the scene Sunday, calling the attack, "cowardly," while politicians across the spectrum decried the violence.

Premier Matteo Renzi was due in Bologna on Sunday to campaign for an upcoming constitutional referendum. Bologna's mayor told Sky TG24 he doesn't think the blast was related to the referendum campaign.