A "finely balanced" investigation into the collapse of the CTV building during the 2011 earthquake in Christchurch is into its final stages, but police remain tight-lipped on whether they will press charges.

The six-storey building collapsed and caught fire after the magnitude 6.3 quake struck on February 22, claiming the lives of 115 people inside, including 65 foreign students.

Police legal teams will now take several weeks to analyse their investigation file and two legal reviews by Crown Law and the Christchurch Crown Solicitor.

It is only after careful consideration of these will any decision be made on whether to prosecute or not, Detective Superintendent Peter Read said on Thursday.

"As we have previously stated this has been a very complex, technical investigation involving a range of expert advice to consider," he said.

"While police are unable to pre-empt what the decision will be at this time, we can say that the issues before us are finely balanced."
He said police were "acutely aware of the length of time" the investigation was taking and appreciated the patience of the families of the victims.