A spokesperson from the Nottinghamshire Fire and Rescue Service said: “We currently have 12 fire engines plus two ALP's in attendance.
“The first floor is very smoke logged.
“We will be on the scene for a considerable amount of time so please continue to avoid the area.”
Anthony May, Nottinghamshire County Council’s chief executive, said: “Nottinghamshire Fire and Rescue is currently dealing with a fire at County Hall in West Bridgford.
“The fire alarm sounded at 11.35am and we followed our fire evacuation procedures."Fire wardens cleared the building and the fire service is now managing the incident.
“The safety of our staff is our priority and the arrangements are in place to ensure that they can get home safely.
“We are also working hard to make sure that we can operate our services as normal.
“We would like to thank the fire and rescue service for its swift response and our staff for their quick evacuation.
“We will keep you updated on the situation as it develops.”Staff and the public should check our social media channels for further updates.”