Two more people have been arrested in connection with a large fire at the site of a derelict Victorian brewery.
The blaze started at about 16:35 GMT on Sunday at the 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.
Now a man, 26, and a 44-year-old woman have also been arrested.
All three were taken to Suffolk Police headquarters at Martlesham for questioning.
A Suffolk Fire Service spokesman said the blaze 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 flames.
Station commander Sally Hammond 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.
The stop time for the fire was given as 07:14 GMT on Monday.
Suffolk Police has appealed for witnesses.