Police investigate cause of early-hours blaze and crews from Methwold, Downham Market, King's Lynn, Dereham and Outwell attend

Fire crews from across Norfolk were called to an isolated barn in the early hours of this morning to deal with 700 tonnes of burning grain.

Arsonists are believed to have deliberately set fire to the barn at Salters Lode and destroyed around �133,000 of wheat.

A total of five crews from Methwold, Downham Market, King's Lynn and Dereham were called from 1.23am.

The 50m x 50m barn belongs to Roydon Hall Farms Ltd and a spokesman said the fire had destroyed a year's work as the grain from the harvest was completely lost.

He said the destroyed crop was currently worth around �190 a tonne and there had also been substantial damage to the metal and asbestos barn itself.

Fire crews battled to keep two gas tanks at the rear of the barn from igniting in the blaze.

A police crime scene investigation officer was called to the site while a crew from Outwell fire station remained on the scene to oversee the damping-down process.

Watch manager Kenny Bright said the smouldering remains of the grain retained heat and fused together into blocks before burning in a similar way to charcoal.

'It can burn for quite a while and we use a foam in this case to keep it from flaring-up again,' he said.

Police are warning farmers in the area to keep an eye on their outbuildings and ensure they are secure.

Fire crews in the area have also been attending an unconnected straw stack fire between Walsoken and Barroway Drove which started on Saturday.

Two teenagers have been arrested and bailed following the blaze which saw teams from Outwell, Wisbech, Downham Market and King's Lynn called to the scene.