A large fire at Belfast's former Crumlin Road courthouse is believed to have been started deliberately, the fire service said.
Around 25 firefighters, three appliances and an aerial appliance tackled the blaze.
It started in the early hours of this morning.
The Northern Ireland Fire and Rescue Service said the cause is believed to be "deliberate ignition".
The courthouse closed in 1998.
It was in use for around 150 years and connected via an underground passageway with Crumlin Road Gaol.
It has planning permission to be converted into a hotel and has been put up for sale by Liverpool developer Signature Living.
Shane Quinn, Development Manager of BBT, said: "Unfortunately, we’ve grown all too used to historic buildings in the city being destroyed by fire. But, as we saw after the Bank Buildings fire, historic buildings are often at the very heart of our city’s lives and hold huge meaning for people. We all have to recognise that heritage buildings aren’t about the past.
"Everyone in Belfast now has a responsibility to make sure that we double our efforts to find a long-term use for the Crumlin Road Courthouse. No building is beyond saving. The Trust believes that whilst last night’s fire is devastating for the city to wake up to, with determination and the involvement of local people, we can make sure heritage is at the heart of our city’s regeneration."
Firefighter at blaze at derelict Crumlin Road courthouse in North Belfast.
— Q Radio News (@qnewsdesk) June 1, 2020
The fire started before 3am this morning with 25 fire officers attending the incident @NIFRSOFFICIAL @nifrseast pic.twitter.com/KRj5eFeQSN