At least seven fire engines were among emergency services tackling the blaze at Frogmore Paper Mill at around 3.30pm on Saturday.

Herts Police have this morning (Monday) confirmed it is believed the fire was started deliberately and a boy has been arrested.

“It was reported that a fire had started in a skip, before spreading to a nearby building, a spokesperson said.

Well done to all the crews at yesterdays large fire in Frogmore Paper Mill in #HemelHempstead. They worked incredibly hard to save as much of the building and it’s historic contents as possible. pic.twitter.com/S9zS1SNFUF

— Simon Tuhill (@HFRS_ACFO) January 23, 2022

"Officers attended to put road closures in place while the fire service worked to extinguish the blaze.

“It was deemed that the fire was started deliberately and investigations are continuing.

"A 13-year-old boy was arrested on suspicion of arson and has been released under investigation while enquiries continue.”

The site, which homes the oldest mechanical paper mill in the world, released a statement on social media confirming there had been "extensive damage".

It reads: "Thankfully nobody was injured during the fire, but there has been extensive damage to the Mill's visitor centre.

Following a fire Frogmore Paper Mill will be closed to visitors until further notice. Whilst nobody was hurt, there has been extensive damage to the visitor centre. We're grateful for the quick response of @HertsFRSControl and their work to bring the fire under control

— Frogmore Paper Mill (@FrogmoreMill) January 23, 2022

“We're in the process of assessing the damage to the site and our collection, and we're hopeful that our historic working paper machines have survived.

“We're extremely grateful for the quick response of Hertfordshire Fire and Rescue and their work to bring the fire under control. We're working with the police and Fire Service to help determine the cause of the fire.”

A fire service spokesperson said it was called to the commercial premises in Frogmore Road at 3.28pm.

“Over the course of the incident we had 13 appliances in attendance," they said.

Frogmore paper mill fire 💔 #frogmorepapermill #papermillfire #frogmorepapermillfire https://t.co/lTNecvGF80 pic.twitter.com/aXuaaKhSPR

— FutureBleeps (@FutureBleeps) January 22, 2022

“One industrial unit approximately 50m x 10m well alight.  Firefighters used breathing apparatus, jets and hose reels to tackle the blaze.

“Fire was under control at approximately 6.30pm but crews remained on the scene for dampening down.

“Stop message 6.35am on Sunday 23 January."

They added: "We are now working jointly with the police to determine the cause of the fire, which is currently listed as deliberate.”

At the time Hertfordshire County Council, which runs the fire service, had advised people to keep their windows and doors closed.

There were also several road closures.