O’Rourke started demolition work last October at the 1970s shopping centre which will be replaced with a modern retail and office complex.
No-one was injured in the collapse which affected two structural bays of a car park on the site.
A Laing O’Rourke spokesperson said: “During demolition of the multi-storey car park, two floors of two structural bays collapsed into the demolition exclusion zone.
“The exclusion zone is an area where personnel are not permitted and specialist machines work from the perimeter on the demolition of the building.
“The exclusion zone is further protected by a safety zone where only trained personnel are permitted.
“These measures are put in place to keep members of the public and site personnel safe at all times and allow for the unpredictable nature of demolishing buildings of this age and condition.
“As a result of these measures nobody was injured by this localised collapse.”