Britain and America are on high alert this weekend for fear of renewed attacks in the wake of last Tuesday's strikes on New York and Washington.
Acting on various leads that have emerged through the investigation, the US Federal Bureau of Investigation has sent out advisories with particular emphasis on water and power facilities.
John Ashcroft, the US Attorney General, was reported yesterday to have phoned officials in Massachusetts warning of a possible terror attack in Boston in the next few days.
Public access to landmark monuments, such as the Golden Gate Bridge in San Francisco, is being limited or halted. And America's Federal Aviation Authority has ordered all commercial airliners to avoid the airspace above major sporting fixtures this weekend.
According to Boston's Mayor, Thomas Menino, and other public officials, Mr Ashcroft's decision to call for heightened security was not based on any specific threat.
However, law enforcement and intelligence officials have said they believe the events of 11 September were intended to be just the beginning of a campaign against the United States, lasting several days and involving many different sorts of targets.
The FBI has learned that today, 22 September, has emerged as a key date because five suspected associates of the hijackers were booked on the same United Airlines plane from San Antonio to Denver. That flight has now been cancelled, as much for reasons of slumping business as security, the airline said.
Sir John Stevens, the Scotland Yard Commissioner,has said there was no specific threat against London. But when he was asked, who was the biggest US ally, and what could be the next biggest target, he said: "It's got to be here."
Bob Graham, the chairman of the Senate Intelligence Committee, has indicated that a second wave of attacks might involve a major infrastructural disruption, such as blowing up a bridge or poisoning a city's water system.
Water authorities from Connecticut to California were on particularly high alert.
It is not clear whether the FBI and other agencies have cracked down on the criminal network to prevent further mayhem – there have been a handful of arrests so far, although dozens of others have been taken into custody for questioning. It is also not clear whether 22 September was intended to be a second day of attacks – a fallback date in case the first wave had to be called off – or simply a decoy to frighten people and confuse the investigation.
In France yesterday seven people were rounded up in the Paris suburbs at dawn and held in connection with a suspected plot to attack US targets in France.
The seven, who were not identified, are believed to be linked to Djamel Begal, a French Algerian arrested in Dubai in July, who has told investigators of a plan to blow up the US embassy in Paris.
Meanwhile, The New York Times, reported that the cost of last Tuesday's attacksmay have been as little as $200,000.Reuse content