Around 30 people were evacuated from the Central Government Offices in Tamar on Friday following a fire.
Police received reports at around 12.15 pm that a computer had caught fire at the West Wing and firefighters were dispatched.
Faulty cables are suspected to have sparked the blaze.
Online footage showed flames and smoke billowing behind a computer screen, next to a landline telephone, and staff leaving the scene.
No casualties have been reported so far.