Tony Martin 'held over gun possession'
Farmer Tony Martin, who was jailed after a fatal shooting in 1999, has been arrested on suspicion of illegal firearm possession, the BBC understands.
Police said a man, 71, was arrested on Thursday morning in the Wisbech area of Cambridgeshire.
Officers searched a property at Emneth Hungate in Norfolk.
Mr Martin lived alone at a farmhouse in Emneth Hungate when he caught Brendon Fearon and Fred Barras inside.
He fired his shotgun towards the intruders, killing 16-year-old Mr Barras.
Norfolk Police said they completed their search of the property and the arrested man had been freed on bail until late February while inquiries continued.
The 1999 case provoked a national debate about the measures homeowners can take to defend their property.
Mr Martin was released in 2003 after serving two-thirds of a five-year sentence.
He was found guilty of murder in 2000, but his conviction was reduced on appeal to manslaughter.
At the scene: Louise Hubball, BBC News
On a cold, sunny day - the last day of 2015 - the Norfolk village of Emneth Hungate was bustling with activity in stark contrast to its remote and rural surroundings.
As sheep grazed in the fields opposite, police officers could be spotted along a secluded track.
I saw four, 4x4 police vehicles leave the scene, with a police dog van, a grey police car in Norfolk Constabulary livery and a van with three officers outside, parked along the lane.
Norfolk police said, in a statement: "As part of a planned operation, a 71-year-old man has been arrested in Wisbech this morning on suspicion of possession of an illegal firearm.
"A police search of a property in Emneth Hungate is currently being undertaken."
An eyewitness, who did not want to be named, reported seeing police vehicles, a helicopter and armed officers in the village.