An exclusion zone around Suncorp Bank in the Townsville CBD has been revoked, two days after concerns were raised over the building being unstable.

A piece of concrete on the building's facade slipped several centimetres and was spotted on Tuesday, prompted the evacuation of an entire city block.

A smaller exclusion zone was placed around the building before it was extended to the entire city block, which covered about 20 buildings.

The declaration of the exclusion zone, which stretched from Sturt Street, Stokes Street and Denham Street,  was revoked at 5.30pm on Thursday.

Structural engineers organised by the building owner were assessing the building, according to Townsville City Council.