Police have completed their criminal investigation into the fatal CTV building collapse and are now seeking legal advice on whether charges will be laid.

The building collapsed during the February 2011 quake, claiming 115 lives.

Detective Superintendent Peter Read said today that the police report into the collapse was complete and had been passed on to the Christchurch Crown Solicitor for review.

“The file will then undergo further legal review before police make a final decision regarding any prosecution,” he said.

“The investigation report includes expert engineering advice which has been subject to overseas peer review.”

Read said police were still awaiting further commentary around some of the engineering advice. However, that had been delayed due to the impact of the November earthquake and the availability of the relevant engineering experts.

The Crown Solicitor’s review would progress further once that commentary was received.

“I am very mindful of the length of time this process is taking and the effect this is having on the families of the CTV victims,” Read said.

“I can only reiterate again that this is a very complex, technical investigation and our priority must be to ensure it is conducted methodically and thoroughly, taking into account all the relevant expert advice, before we can reach a final decision. “

Read could not put a timeframe on when a decision would be announced, but it would be next year.

“The decision will be communicated first to the families and then publicly,” Read said.

“The families were advised of this update earlier today, and I again thank them for their ongoing understanding of the situation.”

Investigators have interviewed more than 100 witnesses and raided the offices of Engenium Consulting Engineers, formerly Alan Reay Consultants, which designed the ill-fated building in the mid-1980s.

Police also engaged engineering contractors to examine the site earlier this year, and worked with engineering consultants Beca to make replicas of the structure to test its critical elements.

In 2012, a Royal Commission of Inquiry found serious errors by engineers, structural designers and the Christchurch City Council.

After the report's release, families and friends of the victims called for legal action to be taken against those responsible.

The commission said Dr Reay should have recognised that his employee David Harding was working beyond his limits when designing the building in 1986.