Terror police investigating a threat to an Islamic event have released eight more men from custody.

The UK Ijtima, which took place at Shurbland Hall in Barham, had around 15,000 people in attendance before it was forced 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 July 12 and 13.

A woman was also arrested on suspicion of assisting an offender, and the thirteenth man was arrested on Thursday on suspicion of an offence under section 5 of the Terrorism Act 2006.

The law dictates that individuals arrested under the Terrorism Act are only able to be held for seven days from their arrest.

Four people were originally released on Tuesday, and another seven were released yesterday without charge.

Police confirmed that one man was released on bail under strict conditions pending further investigation.

The force confirmed that the investigation involved searching homes and vehicles, and over 30 devices were seized.

After the searches, a 42-year-old man was charged with two counts of possession of offensive weapons, extendable batons, and possession of a stun gun.

The charges are not believed to be connected with the alleged threat on UK Ijtima.

He has been remanded in custody to appear at Reading Magistrate’s Court on Monday.

A major incident was declared as the arrests took place in 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.

“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 Labour councillor on Ipswich Borough Council who worked to help organisers through the administration work for the event, told The Daily Mail that police had told organisers “to wrap up because there's a credible threat".

He continued: “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.”