The fire broke out at the Student Lodge on Player Street on Monday afternoon.
Fire group manager David Stevenson said it was proving to be a "very difficult fire to tackle because of a number of hidden voids" in the old building.
Students were evacuated on Monday. Residents of nearby terraced housing are now being moved as a precaution.
Flames could be seen coming from the roof of the building in Radford earlier.
Mr Stevenson said a cordon around the scene had had to be widened because high winds were blowing around debris.
The fire is thought to have started between the third and fourth floors.
Part of the building is occupied, but about three quarters is still under construction. Builders who were working on the site were evacuated on Monday.
Crews from Leicestershire and Derbyshire are also at the scene.
The accommodation block is owned by a private landlord.
About 60 firefighters are still at the scene of a blaze at a student accommodation block in Nottingham's former Player's cigarette factory.