A computer virus brought chaos to Sussex Police today, leaving the majority of the force's 3,000 officers plus support staff staring at blank screens.

Emergency services were not affected but virtually every administrative job carried out on computers was halted by the Nachi worm.

Members of the public reporting accidents or crimes were having their details taken with pen and paper.

Some calls to stations via the non-emergency number 0845 6070999 were delayed as operators transferred calls manually.

Police radios were unaffected and officers still expected to arrive at scenes of crimes in roughly the same time as usual. But the virus was causing headaches at every station and office.

There was little information available for crime victims calling for updates or for people with lost-and-found queries.

Information officers were unable to write Press releases and typists were unable to input witness statements.

The problems caused by the virus, which exploits a loophole in Windows software and slows operations to a snail's pace, were starting to have a knock-on effect today.

Officers with cases stored in computers were unable to retrieve them and there was a danger some court hearings might have to be adjourned.

The virus - also known as Dirty Harry or Welchia - entered the Sussex Police system at noon yesterday and may take the rest of the week to fix.

A force spokeswoman said: "The virus is not thought to have come through an email. It could have been passed on through an infected laptop.

"The important thing to stress to the public is that officers are working normally and all emergencies are being responded to. No staff are being sent home."

Computer technicians worked through the night but most of the force's 1,000 terminals were still switched off today.

It was impossible to tell which terminals had been infected, meaning all hard drives would have to be cleaned.

The force's two main computer centres in Haywards Heath and Brighton were being swept first. Next on the priority list would be incident management centres, followed by station computers.

One insider said: "It's crazy today and it could be Friday before things are normal."

The Nachi worm has been causing havoc in Eastbourne Borough Council's computer network too.

Staff admitted frontline services such as benefits and council tax had been hit after technicians were forced to shut all computers down. They said systems were back on today.

A statement said: "IT specialists have been working continuously over the bank holiday weekend to minimise disruption.

"Some services are still experiencing a few residual problems that stem from the virus and these outstanding issues are being addressed. The council would like to apologise for the inconvenience."

Last week we reported how East Sussex County Council staff had been forced to switch off 3,500 terminals in an attempt to stop the virus spreading.