More than 30 firefighters have been working through the night to tackle a fire at the Old Town Hall in St Paul's Square, Bedford.
A member of the public dialled 999 after seeing smoke coming from the six-storey 1960s office block at around 3am.
Fire crews from Bedford, Kempston, Harrold and Sandy worked through the morning to tackle the fire.
The Old Town Hall is a concrete building, which is no longer in use and is in the process of being demolished.
Local roads were closed to assist access for emergency vehicles.
Relief crews were sent from Woburn, Shefford and Biggleswade fire stations to replace crews that had been tackling the fire since 3am.
Six hours into the incident, the firefighting is still ongoing - from inside and outside the building. Firefighters wearing breathing apparatus have been tackling the fire in the stairwell and on several floors inside the building; and also from the aerial platform, outside.
A spokesperson for Bedfordshire Fire and Rescue Service said: "Our firefighters and control staff have been working extremely hard throughout the night to contain the fire.
"Good progress is being made with what is a difficult and complex fire."