THOUSANDS of visitors, set to converge on Dartmoor this bank holiday, are being urged to be extra vigilant as the danger of accidentally starting a fire escalates in the tinder dry conditions.

After weeks of sunshine any carelessness in dropping a cigarette end or failing to put out a barbecue or camp fire properly can rapidly lead to a major outbreak.

During April there have already been half-a-dozen fires, including Easter Sunday's 200 hectares blaze at Sittaford Tor, above Postbridge, on the high moorland.

Firefighters from Chagford, Bovey Tracey, Princetown and Tavistock were called just before 1pm and found a mile stretch of grassland affected.

The Devon and Cornwall Constabulary helicopter was returning from Plymouth's Derriford Hospital when the crew spotted the fire around a mile west of Fernworthy Reservoir.

The chopper flew a senior firefighter to the remote location to allow them to plot the fire's path and devise a strategy to fight it. A water bowser from Torquay was also called out, and the flames were finally out by 6pm.

Among the others have been a 20 sq m gorse fire at Mary Tavy and a small gorse fire at Brentor, both on Friday.

Some of those fires have been arson and some accidental.

A national park authority spokesman said the swaling season finished at the end of March and a couple of fires this month were illegal burning.

The authority's head ranger, Richard Steemson, said they obviously wanted people to enjoy Dartmoor but would urge them to do what they could 'to help us prevent a fire from breaking out'.

He said: 'We have particular concerns at the moment with the recent spell of exceptionally dry weather, which has made moorland vegetation particularly vulnerable to fire risk.

'Moorland fires can spread very quickly and can be devastating to the landscape and its wildlife, and to ground nesting birds at this time of the year.'

Mr Steemson added that discarded cigarettes, matches, lighters or glass bottles could start fires.

If portable barbecues were being used, they should be placed on a rock to prevent damage to vegetation.

'Care should also be taken with camping stoves and fuel. All rubbish should be taken home and disposed of responsibly.

'Anyone seeing a fire should report it quickly to the fire service by phoning 999 so that they could take the appropriate action,' said Mr Steemson.