By Adam Blenford
Key evidence in the trial of 29 Italian police officers charged over violence during the 2001 G8 summit in Genoa has vanished, police say.
Police are accused of brutally mistreating Genoa protesters
Two Molotov cocktails allegedly planted by police in a school used as a base by anti-globalisation protesters can no longer be found.
The bombs are seen as crucial physical evidence against many of the defendants in the high-profile trial.
The police are accused of brutality and perjury over a raid on the Diaz school.
The petrol bombs - expected to be a key piece of evidence in the case - were due to be presented in court this week.
Prosecutors now fear that the case could collapse, allowing many of the high-ranking defendants to walk free.
Case at risk
The apparent disappearance of important evidence sparked strong reactions within Italy.
The presiding judge called for an immediate explanation.
The Reform Communist party - part of Prime Minister Romano Prodi's centre-left coalition government - has asked for a parliamentary investigation.
Mark Covell, a British journalist who suffered serious injuries in the Diaz raid, told the BBC News website the disappearance could endanger the whole trial.
"They have spent 20 million euros (£13m) on this and if these Molotov cocktails aren't found it could all be for nothing," he said.
"I'm a bit shocked and numb at the state of the Italian judiciary.
"But we can't calculate the full impact of this yet. We will have to wait and see."
One police officer, Francesco Borre, told Italy's La Repubblica newspaper that police routinely kept records of what they received and handed over.
He said he believed the responsibility for keeping the Molotov cocktails rested with Genoa's police, known as the Digos - the same unit under investigation by the court.
There were riots by violent protesters before the Diaz raid
The secretary general of the Italian police union, Claudio Giardullo, held out hope that the trial could continue.
"Because the Molotov cocktails were actually photographed before they disappeared, the material need to have the bottles has been lessened," he told the BBC.
"It is up to the magistrate to decide whether the evidence is fundamental to the trial.
"Police will hold an investigation about this - it is in their own interest," he added.
The trial centres on a raid carried out on the night of 21 July 2001.
Nearly 300 officers, most dressed in full riot gear, forced their way into the Diaz school, which was being used as a base by anti-globalisation protesters.
Dozens of people were injured in the raid, as police also smashed windows and destroyed computers.
The two Molotov cocktails found inside the school were originally cited as evidence that the protesters were planning violence.
But reports soon emerged that the bombs were planted in the school by police themselves.
Prime Minister Prodi has made the swift conclusion of the trial a priority, and has promised to investigate the conduct of the police.