Inmates have been evacuated from a Suffolk prison after a fire broke out inside.
Prisoners at HMP Highpoint were relocated to a safe location after ten crews were sent to fight the blaze at 2.40pm, Suffolk Fire and Rescue said.
Two more fire crews were sent from Cambridgeshire.
The fire was found in a timber and brick structure - fire crews used thermal image cameras and jets to stop it from spreading.
'As well as extreme heat, firefighters are faced with the additional challenge of difficult access and a complex internal layout,' a fire service spokesperson said.
HMP Highpoint is a category C men's prison with 1,300 inmates near Stradishall.
All prisoners were reportedly accounted for after being evacuated.
The East of England Ambulance Service said there were no reports of casualties but added paramedics would remain on site to support fire crew.
HMP Highpoint pictured last year as work on its expansion began. Fire crews were sent to a large fire at the prison on Friday afternoon
Suffolk Fire and Rescue said the fire at the prison was a 'larger' blaze and was split into sections for different crews to tackle systematically.
A spokesperson said earlier: 'A fire has broken out in a prison block. Upon first crews' arrival, staff had already evacuated the building and relocated occupants to a safe location. Prison staff have confirmed that all persons have been accounted for.
'Firefighters are currently using breathing apparatus, one hose reel jet, one covering jet and a thermal image camera to tackle the blaze, which is well developed.
'The officer in command has given an instruction for the fire to be sectorised, which is a tactic deployed by firefighters when tackling larger fires – the fire is effectively split into sections, with crews assigned to each section. This helps firefighters maintain control, improve safety, streamline communication, and ensure the incident is managed effectively as it grows and evolves.'
Crews from Bury St Edmunds, Ipswich East, Ixworth, Clare, Newmarket, Long Melford, Sudbury, Woodbridge and Haverhill had arrived to tackle the fire.
A Prison Service spokeswoman told the Daily Mail: 'A fire broke out at HMP Highpoint on Friday afternoon and Suffolk Fire and Rescue Service are in attendance.
'Staff have taken immediate action and all staff and prisoners are accounted for, with no injuries reported.'
Last year it was reported HMP Highpoint would increase its capacity by more than 50 per cent by 2027 to become 'the UK's largest' jail, according to the Ministry of Justice.
Three four-storey housing blocks were set to be built as part of the 700-place expansion.
It is not clear where Friday's fire broke out.
This is a breaking news story with updates to follow.