Police say they need more information before they can make a decision about whether someone is criminally responsible for the collapse of the CTV building in Christchurch.

115 people died when the building collapsed in the 2011 February earthquake.

More than 100 witnesses have been interviewed, and search warrants executed as part of the investigation.

Police announced in September this year that part of the investigation involved a mini-reconstruction of the building.

Detective Superintendent Peter Read says that's taken longer than anticipated, and police expect to get the full analysis of that testing early next year.