Four fire engines have been sent to a fire at the old planning offices at South Hill.
A total of 18 firefighters are on the scene in St Helier this afternoon (3 January).
An Incident Command Vehicle and Fire Duty Manager have also been dispatched.
The fire is said to be on the first floor of the former offices.
Footage posted online shows smoke coming from the building.
People are being asked to avoid South Hill, as the road is closed at both ends.