Police and trading standards officers are to patrol the protection zone around the two Surrey farms affected by the foot-and-mouth outbreak.
The patrols follow concerns some people are ignoring the restrictions and tearing down signs indicating footpaths which have been closed off.
Stroude Farm and Hardwick Park Farm, near Egham, both have the virus.
The strain found at Hardwick Park Farm is the same as that found during the outbreak in August, initial tests show.
Jail and fine possible
The government is being urged to ease some movement restrictions on some animals in England, as in Scotland and Wales.
In Scotland and Wales farmers are allowed to take livestock direct to slaughter, but animals can still not be traded or moved for any other reason. Northern Ireland is not affected.
The two Surrey farms affected are spread over nine areas including Ripley, Shepperton, Staines and Thorpe.
A 3km (1.8-mile) protection zone has been set up around the land, with a 10km (6.2-mile) surveillance zone encircling it, meaning a large part of west Surrey now has restrictions in place.
Environment department sources say a total of 940 cattle and pigs have been culled so far in the latest outbreak.
Surrey trading standards has closed off all the necessary paths and put up warning signs. But there have been reports of people tearing them down.
This weekend trading standards officers along with police will patrol the affected areas, stopping and questioning people transporting animals, walking dogs or riding horses.
Those prosecuted could face a £5,000 fine as well as six months in jail.
'Anxious times'
Government vets are expected on Saturday to continue their inspections on the two farms.
Farmers said the latest outbreak was "much worse" than last month's, because it had come at a time when livestock farmers needed to move their animals, and send them to market.
WHAT CONTROL ZONE MEANS
Vice chair of the Surrey branch of the National Farmers' Union, Hugh Broom, said it was an anxious time.
"Everything was going quite well at the beginning of this week in the sense that life had pretty much got back to normal - markets, sales, movements had all resumed," he said.
"Then come Wednesday morning it was a real kick in the teeth when we were told there was another outbreak in the county.
"So it is anxious times - it's anxious times for farmers in Surrey and indeed for farmers right across the UK, because of the movement restrictions that are in place.
"But obviously they are necessary at this stage if we're going to get on top of this disease once and for all."
EU ban
The total number of farms where the disease has been found in 2007 now stands at four.
Stroude farm is about 10 miles from the Pirbright research complex - blamed as the source for the foot-and-mouth outbreaks at two farms last month.
Scientists investigating the disease are working on the possibility it was carried by soil or through the air, and was not a water-borne transmission.
WHY IS THE VIRUS BACK?
The disease was confirmed on Wednesday only a week after the previous restrictions on cattle movements were lifted.
The government is facing criticism that it was too quick to declare Britain foot-and-mouth free last week.
The European Commission has banned all live animals susceptible to foot-and-mouth from being exported from Britain. Northern Ireland is exempt from the ban, and can export freely.
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