Advice for businesses that are worried about the threat of chemical or biological attacks has been posted on the Thames Valley Police website.

The security information has been prepared under the force's Operation Resilience, activated in the wake of the US terror attacks of September 11, and follows enquiries from concerned bosses.

It gives advice on handling suspicious packages, reviews access to and controls of water tanks, air conditioning systems and post rooms, and suggests what to do in the event of contamination by a suspected chemical or biological agent.

But the information plays down fears of the likelihood of a chemical attack in the area.

A spokesman for Thames Valley Police said: "This information is in response to enquiries. It is definitely not scaremongering."

The advice was issued by Assistant Chief Constable, Steve Love, who heads Operation Resilience.

He said: "Thames Valley Police have worked hard since September 11 to ensure our operational capabilities are as well prepared as they can be.

"We currently know of no specific threat to the communities within the Thames Valley Police area.

"However, events in other parts of the world naturally make us all more aware of what is going on.

"We urge everyone to remain vigilant and calm. These qualities have defeated terrorists and criminals in the past and they will again."

The key advice to businesses is to prevent unauthorised access to air conditioning plant rooms and water storage tanks, and procedures for checking suspect packages.

Procedures in the event of a suspicious item being received or opened are also detailed, as are actions to take with someone who may have become contaminated.

The full advice to local businesses is available from www.thamesvalley.police.uk