Farmers and land owners across Norfolk must remain vigilant against the threat of raves over the festive season, police have warned.Officers fear individuals may exploit the holiday period to use large buildings such as empty warehouses and offices, farm outbuildings and remote land to host unlicensed music events.

Farmers and landowners must stay vigilant to the threat of raves over the festive season, police warned last night.

Norfolk Constabulary fears rogue organisers may exploit the break to use empty warehouses and offices, farm outbuildings and remote land to host unlicensed music events.

Supt Mick Kirkham said raves were anti-social and caused a lot of distress to neighbours.

Organisers did not arrange to ensure the heath, safety and security of people who turned up to them, either.

The force is using intelli-gence gathered throughout the year.

It has intervened at various high-profile events in 2007, including the one at Yarmouth that led to clashes between officers and rave-goers.

Police say that the telltale signs for businesses and farms to watch out for include:

Large convoys of cars grouped together in car

parks.

Vans and trucks suitable for carrying sound equipment making their way to sites.

People who take bookings for village halls and community centres at short notice should also be wary, say police.

They are urged to ask probing questions as to people's motives for hiring rooms, obtain precise numbers of those attending and jot down a land-line contact telephone number and address of the organisers - which they should verify before confirming the booking.