The police's criminal probe into the February 2011 earthquake has been slimmed down to now focus on just four of the 24 fatal building collapses.

Investigators have already interviewed more than 100 witnesses and raided the offices of Engenium Consulting Engineers, formerly Alan Reay Consultants, which designed the Canterbury Television (CTV) building at 249 Madras St which collapsed in the magnitude 6.3 shaking, claiming 115 lives.

Police had initially been looking at another 23 building collapses that resulted in deaths as part of its criminal investigation.

But now, after 20 sites were investigated and criminal liability ruled out, the investigation is focussing solely on the CTV building and just three other sites: Southern Ink Tattoo parlour at 593b Colombo St, Ballantynes Carpark Buildings at 43 Lichfield St, and St Christopher's Book Market at 7 Riccarton Rd.


Yesterday, Police Minister Judith Collins confirmed the four sites were being probed in response to a February 26, 2016 written question from Labour MP Megan Woods.

The minister today referred all enquiries to police.

Apprentice tattooist Matti McEachen, 28, was killed by falling masonry while trying to flee the Southern Ink tattoo parlour.

Linda Arnold, 57, had been sitting in her car outside the Ballantynes car park building when a concrete panel fell from the building and crushed her to death.

Henry Ross Bush, a bricklayer, died when the facade of the Riccarton Rd secondhand bookshop collapsed during the earthquake.

In December, Detective Superintendent Peter Read confirmed the criminal investigation into the six-storey concrete CTV collapse is ongoing, with no decision expected until next year.

At the time, he said police were unable to put any firm timeframes on when a final decision will be announced on whether charges would be laid, however they anticipated a further update "in the first quarter" of 2016.

In 2012, the royal commission of inquiry found serious errors by engineers and structural designers when the ill-fated Christchurch office block was designed in the mid-1980s.

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.

Investigations by Canterbury Police detectives into the collapse of four buildings during the 2011 earthquake, including the CTV building, have been "underway for some time", a police spokesman said today.

The outcome of each investigation will be subject to legal review by the Crown Solicitor's office before police make any final decisions on criminal liability.

"We expect the outcome of these investigations to be announced publicly," the police spokesman said.

"At this stage we are unable to put a timeframe on when these investigations will be completed.

"We can however say that we expect the CTV investigation will take the longest, given the particular complexities involved with this enquiry."

Updates on the CTV building investigation will be made available on the police website.