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.

Bulls ease into next FA Cup qualifying round
London man jailed for fraudulent purchases in Jersey worth over £10.5k
Report reveals what islanders are earning
Jersey's Siena Stephens gets Supertri wildcard
Spaghetti and ale on the menu at Gorey Fete
Police seek information after assault sent 61-year old man to hospital
Economic Development Minister apologises for minimum wage comments
Jersey's GCSE pass rate rises to 77.1%