Firefighters were called to a second blaze at the Masons pub in Victoria Street, Ipswich, in the early hours of this morning.
Two units from Princes Street were called to the incident, which follows an earlier fire tackled by eight crews, at around 1.27am.
A Suffolk Fire and Rescue Service spokesman said an investigation is underway into the cause of both fires.
A re-inspection of the building was carried out at 8am today, and crews found the second fire had started in a back room.
Thick black smoke was seen billowing from the derelict pub during the first fire, which saw three appliances from Princes Street, two from Ipswich East, two from Woodbridge and one from Holbrook sent to the scene shortly after 8.30pm yesterday.
Firefighters used an aerial ladder platform to remove roof tiles and damp down the fire which was on the first floor and in the roof space.
It is understood firefighters had to fight the flames from the roof after the building’s stairs collapsed.
The spokesman confirmed a search of the building was carried out by firefighters wearing breathing apparatus, but no-one was found inside.
The fires come less than two months after a blaze at the building was put down as suspected arson.
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