Six fire crews were sent to tackle the blaze at the Royal Doulton site in Nile Street, Burslem, Stoke-on-Trent, during Friday evening.

The building, now a visitor centre, has been the subject of previous attacks by arsonists.

Investigators said they would keep an open mind into the latest fire's cause but arson would be a line of inquiry.

Firefighter Kevin Stubbs said: "Firefighters from Burslem and Hanley have attended quite a number of fires in and around the site and a number of them were deliberate.

"So obviously that will be one line of inquiry."