A shadowy Mafia organisation is suspected of a bombing that killed a 16-year-old girl and injured up to 10 other students in the southern Italian city of Brindisi on Saturday.
Police and paramilitary Carabinieri were raiding the homes of suspected mafiosi belonging to a crime group known as the Sacra Corona Unita, or United Sacred Crown, and checking their whereabouts prior to the attack.
Two gas canisters equipped with a timer device exploded outside the Morvillo-Falcone vocational institute, which is named after an anti-Mafia prosecutor, Giovanni Falcone, and his wife, Francesca Morvillo, a judge, who were blown up by Sicily's Cosa Nostra Mafia almost exactly 20 years near Palermo airport.
The fact that the bomb went off just days before the 20th anniversary of the assassinations, on Wednesday, may have been a coincidence, given that Cosa Nostra and Sacra Corona Unita are quite separate Mafia groups.
Sacra Corona Unita, based in the region of Puglia, the heel of the Italian boot, is the least known of Italy's four Mafia groups.
It was founded in the 1970s and has made huge profits from gun-running, smuggling and extortion, although its power is believed to have waned in recent years as a result of police crackdowns.
But it has ready access to explosives through its links with organised crime in the Balkans, just across the Adriatic.
While the Italian government cautioned against jumping to conclusions about who might be behind the attack, local officials had little doubt, blaming it on the group and saying it may have been a reprisal for recent police operations.
"It was a Mafia attack," said Nicola Fratoianni, a regional official. "A bomb placed in front of a school bearing the Falcone name is a clear message from the clans - a reprisal to recent police operations."
Ten days ago police conducted a raid in which they arrested 16 alleged members of Sacra Corona Unita, charging them with extortion, illegal weapons ownership and Mafia association.
Many of the pupils at the school, including the teenager who was killed, were from the nearby town of Mesagne, one of the strongholds of the Mafia group.
The attack may also have been timed to coincide with an anti-Mafia procession that was due to have been held in Brindisi on Saturday.
According to another theory being pursued by police, it may have been connected to a failed attempt by godfathers a few days ago to blow up the head of an anti-Mafia association in Mesagne with a car bomb.
"We have seen a resumption of criminal Mafia activity in and around Brindisi recently after leaders of Sacra Corona Unita were released from jail," said Alfredo Mantovano, an MP from the conservative People of Freedom party of Silvio Berlusconi, the former prime minister.
Prosecutors pointed out, however, that Mafia gangsters normally carry out attacks against rival mobsters, prosecutors, police and courthouses, and that it was unusual for them to hit such a soft "civilian" target.
The bomb, believed to have been planted on a low wall in front of the school, went off around 7.50am local time, when students were arriving for Saturday morning lessons.