A father and son were being held today under the Terrorism Act after the discovery of traces of what is thought to be the deadly poison ricin at the house of a suspected white supremacist.
Anti-terror officers raided the home of Ian Davison in Myrtle Grove, Burnopfield, County Durham on Tuesday.
Since the 41-year-old former pub DJ's arrest under the Terrorism Act 2000 forensic officers have been examining the terraced property.
Also arrested in Tuesday's operation was Davison's teenage son Nicky, 18, who was held on suspicion of inciting racial hatred following a swoop at his home in Grampian Court, Annfield Plain.
However, he has since been re-arrested and is also now detained under the Terrorism Act in West Yorkshire.
Assistant Chief Constable Michael Barton said: "Specialist police officers have been carrying out a meticulous search of the property which is a 'two-up two-down' terraced house.
"They have uncovered a substance, which we believe has traces of Ricin.
"It was in a sealed jam jar that has been kept in a kitchen cupboard - apparently for up to two years.
"Tests on the substance were carried out at a Government laboratory in Edinburgh on Thursday."
Speaking at a press conference at the force HQ in Durham City, Mr Barton added: "Specialists from the Ministry of Defence establishment at Porton Down are due in Durham today to discuss the safe transfer of the substance to their laboratories for further tests.
"That transfer will take place under a police or military escort and their report should be finalised in the next few days.
"Purely as a precautionary measure the search of the house has been halted for the time being. The property is cordoned off and remains secure and under police guard.
"Specialist help has been offered by government agencies. Durham Police is liaising with them and will continue to work closely with our local partners and other services until this is over."
Davison was being quizzed by officers from Durham Police and the North East Counter Terrorism Unit at a police station in West Yorkshire.
Also arrested in Tuesday's operation was Davison's teenage son Nicky, 18, who was held on suspicion of inciting racial hatred following a swoop at his home in Grampian Court, Annfield Plain.
However, he has since been re-arrested and is also now detained under the Terrorism Act in West Yorkshire.
Durham Police said the arrests followed a long-running intelligence-led operation against extreme right-wing activity.
Mr Barton continued: "Because of the find the search of the house will be continued by officers in specialist protective clothing.
"That search is likely to last for several days. There may be other suspicious items in the property.
"Staff are on a heightened state of alert to what could be found and a cordon will remain in place until experts confirm there are no further suspicious substances at the address.
"Immediate neighbours to the house, who are fully supportive of the police operation, are being spoken to about the latest developments.
"They are being given advice and will be kept fully informed. On scientific advice we are told there is no need for them to be evacuated.
"I would again like to reassure people in Burnopfield that the substance found was sealed in an airtight container prior to its removal.
"As such no one is believed to have been exposed to the substance or be at risk of any potential ill-effects. We do not believe that there is any risk to public health.
"Public safety remains our priority and we are grateful for the ongoing patience and co-operation of local people while these inquiries are concluded."
Ricin has been used in plots by suspected al Qaida operatives and can be fatal if when inhaled, ingested or - most dangerously - injected.
It is made from the beans of the castor oil plant and is 6,000 times more poisonous than cyanide.
Experts say that 70mg or two millionths of an ounce - roughly equivalent to the weight of a single grain of salt - is enough to kill an adult.
To cause mass casualties ricin would need to be either used in aerosol form or as an additive to food or drink.
Ricin was used by the Aum cult on the Tokyo subway system in 1995 in an attack that left 12 people dead.
