The historic Crumlin Road courthouse in Belfast has been extensively damaged in a suspected overnight arson attack.
The court, which closed for business in 1998 has been targeted before, the last time in March this year.
The Fire and Rescue Service said today a large amount of damage had been caused throughout the listed building by the blaze, which they fought for seven hours from shortly after 11pm.
Michael Graham of the Fire and Rescue Service said: "We believe the fire was started deliberately. There is a large amount of damage right through the property - the vast majority of the centre section of the roof is completely burned away.
"Due to the skill of the fire fighters we managed to prevent it spreading through the entire property."
The Police Service said said they too suspected the fire was started deliberately, but because of concerns over the safety of the building engineers had been called in to carry out an examination before anyone searched to confirm the fire was arson.
The Crumlin Road was closed over part of its length for more than five hours because of the fire.
The Grade B listed building, designed by Sir Charles Lanyon, opened in 1850 and was the scene of many hundreds of terrorist trials through the first three decades of the Troubles.
A tunnel leads from the dock of No 1 court under the road to the Crumlin Road prison which is also closed and now a tourist attraction.
When it closed in June 1998 it was put into cold storage and sealed off. Developer Barry Gilligan later bought the property from the Government for a nominal £1. In 2006 he announced plans to turn the building into a luxury hotel but no work was ever started.
In March this year another arson attack resulted in the destruction of some 40 per cent of the court building, but its ornate facade was preserved.