Rome ( CNN ) -- At least one girl has died and half a dozen are injured following a bomb blast outside a school in the southern Italian city of Brindisi , Italian officials said Saturday . Officials have given conflicting accounts of the number killed and injured . Daniela Buccoliero , an official at the Prefecture of Brindisi , a local office of the Interior Ministry , told CNN one 16-year-old girl had died and another six students are injured , two of them seriously . Brindisi Mayor Mimmo Consales and Fabiano Amati , regional minister for Italy 's Civil Protection agency , said there had been two deaths as a result of the blast . Amati said the scene shortly after the explosion was `` dramatic . '' `` There were school back packs and notebooks everywhere . Many windows of the nearby buildings were broken , '' he told CNN . Amati said the police had found three gas cylinders at the site that were detonated with a remote control . The device was concealed behind a trash can by a wall 50 meters from the entrance of the school , he said . `` It 's an attack on all Italians because schools are considered a secure area , '' Amati said . `` It 's the first time in our country that a school is under attack . '' Consales told CNN one of the girls had died in surgery from the wounds she sustained in the blast . Another of the injured is in very serious condition , he said . Italy 's Prime Minister Mario Monti said the government was determined to combat crime and unite the country . He expressed the government 's `` deep sorrow , dismay and outrage '' at what he called a `` most grave and heinous crime '' in a statement from the United States , where he is attending the G8 summit . Monti was informed of the blast during the night , and has been in close contact with Italy 's president , interior minister and other local authorities since . He has ordered the country 's flag to be displayed at half-staff Saturday and for the next three days , and sent a message of condolence to those directly affected by the blast . Italians gathered in front of the Pantheon in Rome and at Plebiscito square in Naples late Saturday to protest the violence and to show support for its victims . Three days of mourning were declared in Brindisi , where schools will be closed through Tuesday . The explosion occurred early Saturday as students were arriving at the school , which offers vocational training , Italy 's ANSA news agency reported . It is not yet clear why the school was targeted or who carried out the attack . Police chief Francesco Cirillo told CNN that the motive is under investigation and that no one has claimed responsibility . Nichi Vendola , governor of the Puglia region where Brindisi is situated , said : `` It could be either a mafia or a political terrorism attack . It 's too early to say . It 's an unprecedented event . '' The Francesca Morvillo Falcone school is named after the wife of a prominent anti-mafia judge , which has fueled speculation that the organized crime group might be behind it . It has been 20 years since Falcone was assassinated in Palermo , Sicily , in May 1992 . The school is located near both the tribunal and the city 's tax collection agency . Italy 's tax collection agencies , called Equitalia , have been targeted by mail bombs , Molotov cocktails and suicides in front of their offices in recent months , with the incidents occurring in the cities of Rome , Livorno and Bologna , respectively . Italy 's interior ministry said this week that it would start to deploy soldiers outside some government buildings because of the current tensions . The local anti-racket commission of Mesagne , a town in Brindisi province , issued a warning last week of heightened threats by both organized crime groups and anarchists against government agencies . An anti-mafia march that scheduled for Sunday will go ahead as scheduled . Journalists Livia Borghese and Barbie Nadeau and CNN 's Joseph Netto contributed to this report .
NEW : Italians gather in Rome , Naples to protest the violence . Prime Minister Mario Monti says the government is determined to fight crime . Six students are injured , two of them seriously , a government official says . It is not yet clear who is responsible or why the school was targeted .