Eight more men have been released from custody as terror police continue to investigate an alleged extreme right-wing threat to an Islamic event held at a Suffolk country mansion. The UK Ijtima – which took place at Grade II-listed Shrubland Hall in Barham, near Ipswich in Suffolk, and had at least 15,000 people attending last weekend – had to close early after a warning from the Metropolitan Police's Counter Terrorism Policing Unit. Three men were arrested on suspicion of conspiracy to commit murder, while another eight were detained under the Terrorism Act 2000 on Monday and last Sunday, July 12. A woman was also arrested on suspicion of assisting an offender, and a thirteenth man was arrested on Thursday on suspicion of an offence under section 5 of the Terrorism Act, 2006. Under law, people arrested under the Terrorism Act can only be detained up to seven days from their arrest. On Saturday night, police freed eight more people from custody. Four people were released on bail on Tuesday, and on Saturday officers confirmed a further seven men were released from custody without charge.Another man was freed on bail with strict conditions pending further inquiries, the force said.It said the investigation has involved searching homes and vehicles, and more than 35 digital devices have been seized. The UK Ijtima, which was held at Shrubland Hall in Suffolk (pictured), had to close early after a warning from the Metropolitan Police's Counter Terrorism Policing Unit Around 15,000 people are understood to have been at the event, which was billed as a time for reflection and spiritual renewal, last weekendFollowing those searches, a 42-year-old man has been charged with two counts of possession of offensive weapons, extendable batons, and possession of a stun gun.The force said the offences he has been charged with are not believed to be connected to the alleged threat on UK Ijtima. He has been remanded in custody to appear at Reading Magistrates' Court on Monday. Thousands of people had attended the gathering at Shrubland Hall near Ipswich, but it was forced to close early after advice from police. A major incident was declared as the arrests – which involved people aged between 27 and 82 – took place in locations around England, including Surrey, east London, Suffolk and Greater Manchester.Commander Helen Flanagan, head of Counter-Terrorism Policing London said: 'This has been a fast-moving investigation after we became aware of information to indicate there was a potential threat towards the Islamic event over the course of last weekend.'Since then, we have made extensive inquiries, but at this time we have found no evidence to support anyone being charged with any offences linked to the alleged threat.'While I know this may still be very concerning to the public and particularly to those in the Muslim community, I want to reassure them that our inquiries are ongoing. Commander Helen Flanagan (pictured), head of Counter Terrorism Policing London, said officers had moved 'extremely quickly' to make arrests 'after becoming aware of a potential serious threat' The religious gathering was being held at this Grade II-listed building by the Tablighi Jamaat, a Sunni Islamic missionary movement founded in India in 1926 Ruman Muhith (pictured), a Labour member of Ipswich Borough Council who was at the event on the first two days, said attendees 'conducted themselves with dignity and respect''Should we identify any potential offences or threats to the public then we will not hesitate to take further action.'I want to reiterate my thanks to the event organisers and to the local community in the area for their continued support and understanding as our investigation continues.' Ruman Muhith, a local councillor who helped guide the organisers through the administrative steps needed to set up the event, said they had accepted police advice to end the event early 'without hesitation'.He said police had told the organisers 'to wrap up because there's a credible threat'.Mr Muhith, a Labour councillor on Ipswich Borough Council, said: 'There was no panic on site because attendees weren't made aware of it (the threat), they were just told it was finishing early after the morning prayer.'The religious gathering was being held by the Tablighi Jamaat, a Sunni Islamic missionary movement founded in India in 1926 and now one of the largest religious movements in the world.The Bishwa Ijtima in Bangladesh draws millions and the Raiwind Ijtima in Pakistan hosts hundreds of thousands. The event is billed as a time for reflection and spiritual renewal and typically involves prayers five times daily. The Hall, which was built in the 1770s and was sold in 2006 by Baron de Saumarez to cover an inheritance bill, was purchased for £6 million in 2009 by Dr Muhammed Farmer, a London-based businessman and founder of the British Institute of Technology.It was chosen ahead of ExCel London and the NEC in Birmingham and promotional material online before the event described it as 'perfectly suited for the gathering, offering vast space for 100k+ attendees and unlimited parking'.The same material said the 'Hazratji will be present' – the title given to the movement's senior leader.