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

Emergency services were first called to Sturt Street about midday and established a smaller exclusion zone around the building.

This was extended about 2pm to encompass the entire city block of about 20 buildings.

Police declared an emergency and issued an update on Wednesday saying the exclusion zone would remain in place until at least midday.

The evacuated city block was encompassed by Sturt, Denham, Walker and Stokes streets.

On Wednesday, Denham Street was expected to open but with no right turn into Walker Street, one lane of Stoke Street was expected to open, Sturt Street was expected to open and Walker Street would remain closed.

Suncorp Bank said it was working with emergency services and the landlord.

"Our priority is the safety of our people and our communities. As soon as we became aware of the issue, we worked with emergency services and the building’s manager to evacuate our people," the statement read.

"Suncorp is a tenant in the building and we, alongside the other tenants, are working with the landlord to ensure that the issue is resolved safely."

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