Three teenagers have been arrested following a fire at the old planning offices on South Hill yesterday afternoon (3 Jan).
Emergency services were called to the scene at 2.08pm, with police and Jersey Fire and Rescue attending. An ambulance was put on standby.
25 firefighters were tackling the flames at the peak of the incident, with four fire engines, an incident command vehicle and fire duty manager also on scene.
JFRS say that while the fire was extinguished it was 'difficult to access'.
The fire service stayed at the building, dampening down flames until after midnight, with roads remaining closed for that time too.
No injuries have been reported and all roads have since reopened.
Paper was set alight in Pier Road toilets as well, and police are linking it to their investigation.

New 'competitiveness' plan to protect Jersey's £3bn financial sector
Fines for 'Jersey Lifts' drivers a step closer?
£225K grant given for clinical trial into heart failure
New school grouping system to address pressures on Education
Jersey to nearly quadruple its protected waters
Broad Street turns a new leaf
Ministers unsupportive of legislation to protect cash-use
Woman, 44, guilty of inappropriately touching a teen at Portelet