The bomb attack which killed a teenage girl and wounded 10 others in the southern Italian town of Brindisi was probably not the work of the mafia, authorities have claimed.
The attack on the Francesca Morvillo Falcone school, a vocational training institute offering courses in fashion, tourism and social services, has horrified Italy.
Thousands have taken to the streets in demonstrations of sympathy for the school and the family of Melissa Bassi, below, the young victim.
"It seems to be the work of a single person," Marco Dinapoli, the Brindisi chief prosecutor, told reporters. He said police already had an identikit of the suspect.
"The most probable hypothesis is that it was an isolated act," he said, but refused to give details about the suspect. "At the moment, we don't understand what the motivation for this massacre might be," Dinapoli said.
Early suspicions pointed at organised crime, largely because the school was named after the wife of murdered anti-mafia judge Giovanni Falcone and the attack took place days before the 20th anniversary of the couple's death in a bomb attack in Sicily.
However as the investigation has proceeded, the idea that either the Sicilian mafia or the local version known as the United Sacred Crown, might mount such a high profile attack has appeared increasingly unlikely.
Dinapoli said investigators had acquired "significant" video evidence which suggested that one man had set off the device, which exploded as pupils at the school were getting off a bus and arriving for the start of lessons on Saturday morning.