Italian police said today they had arrested four Moroccans in possession of large quantities of cyanide and maps of Rome highlighting the location of the US embassy.
Police said they were investigating whether the men, arrested early yesterday in a covert operation, were plotting an attack on the embassy or on Rome's water supply.
Seven Tunisians are on trial in Milan as part of a crackdown on groups suspected of having links to Osama bin Laden and his al Qaeda network. They are also suspected of plotting an attack on the US embassy in January 2001.
The US embassy had no immediate comment on the latest arrests.
As well as around 10 pounds of cyanide and maps pinpointing the embassy and other locations, those arrested were also found with maps of Rome's water network and a stack of counterfeit immigration papers, the police said.
The American embassy, prominently located on Rome's famed Via Veneto, has been targeted for attack on several occasions in recent months.
Even before the September 11 attacks on US cities, the embassy was forced to shut for three days after an intelligence warning of a possible bombing.
Following the attacks on the Pentagon and World Trade Center, the State Department warned again that American symbols in Italy could be targets of attacks.
Italy entered the international spotlight in the fight against bin Laden after US investigators said they believed Milan's Islamic cultural center was al-Qaeda's main European logistics base. Muslim leaders in Italy have denied the charge.
The four arrested Moroccans had been followed by police for days and their detention was related to the arrest of three more Moroccans last week, police said.
The Tunisians on trial in Milan have been charged with intent to commit crimes ranging from the trafficking of arms, explosives and poisonous chemicals to trading in false documents and helping illegal immigrants enter Italy.
Police believe bin Laden sent them to Europe to supervise attacks, including the possible bombing of the US embassy in Rome last month.
Italian justice sources last year released transcripts of telephone conversations in which one of the men on trial in Milan indicated that he was planning chemical attacks in Europe.
In one conversation, the Tunisian told a Libyan associate that there was a plan to "try out" a drum of a "liquid" in France. "This liquid is more efficient because as soon as it opens, people are suffocated," he was quoted as saying.