A man has been arrested following a large fire at the site of a former Victorian brewery.
The blaze started at about 16:35 GMT on Sunday at the derelict Grade II-listed Tolly Cobbold site on Ipswich waterfront, sending plumes of thick smoke into the air.
A 29-year-old was arrested on suspicion of arson later in the evening, police said.
Crews from Suffolk Fire and Rescue remain at the scene on Monday morning.
A spokesman said fire had broken out in some of the higher floors of the building and the roof and 15 crews were sent to the scene, which is the site of a proposed £40m development plan for more than 200 homes and a theatre.
Surrounding roads were closed as crews tackled the blaze.
Station Commander Sally Hammond from Suffolk Fire said there was already an “established fire” when crews arrived.
She said that because it was a derelict building and there were large voids within it, the service did not want to send any crews inside due to a “danger of collapse”.
Instead they undertook “defensive firefighting from the outside”, she said.
Suffolk Constabulary has called for witnesses to come forward.