US fears grow of biological attack

The US says several countries are trying to produce biological weapons

US Secretary of Defence Donald Rumsfeld says the United States is taking seriously the possibility that terrorists might launch an attack using biological or chemical weapons.

Amid heightened fears following the attacks on New York and Washington, the FBI ordered crop-spraying planes to be grounded for 24 hours on Sunday and urged agricultural pilots to "be vigilant to any suspicious activity".

It ought to cause us to recognise that those are dangers that we need to worry about

Donald Rumsfeld, US Secretary of State

It comes after investigators reportedly found a manual on how to operate a crop-dusting plane during a search of the home of an Islamic militant arrested last month.

In New York, army and navy surplus stores are reported to have sold out of gas masks as frightened residents take steps to protect themselves against unconventional attacks.

Speaking on US television network CBS, Mr Rumsfeld said countries blacklisted by America as state sponsors of terrorism "have very active chemical and biological warfare programs, and we know that they are in close contact with terrorist networks around the world".

He said that while there was no evidence the perpetrators of the 11 September hijackings planned to launch a chemical or biological attack, "it ought to cause us to recognise that those are dangers that we need to worry about".

Hijacker

According to US media reports, three men of Middle Eastern origin enquired about crop-dusting planes at an airport in Florida earlier this year.

Authorities fear crop-dusters might be used to carry out a chemical attack

One of the men has since been identified as Mohamed Atta, one of the New York hijackers.

The FBI warned members of a crop-dusters' group to report "any suspicious activity relative to the use, training in or acquisition of dangerous chemicals".

The bureau said it grounded the planes "in reaction to every bit of information and threats received during the course of this investigation".

Aerial crop-spraying resumed on Monday after it was suspended for the second time since the attacks, although flights continue to be barred from the skies around major cities.