WELLINGTON — New Zealand police have extended their investigation into the collapse of a building that killed 115 people, most of them young students from Asia, in the February 2011 Christchurch earthquake.

In September, police said that they hoped to release the results of their probe into the collapse of the city-center CTV building this year, but any decision would now be made next year, Superintendent Peter Read said in a statement Monday.

A phase of the investigation was a physical rebuild and testing of critical elements of the building structure, but this had taken longer than anticipated, given it involved complex technical matters requiring outside experts.

“Police now expect to receive the full analysis of this testing in early 2016,” said Read.

“These findings will form part of the overall investigation, which has already interviewed over 100 witnesses and executed a number of search warrants.”

Police would be in a position to make final decisions regarding any criminal culpability once they had all relevant information, but they would put no timeframe on the process.

The families of the victims had been advised that police would update them in the first quarter of 2016.

“We reiterate that this is a very complex inquiry, and the focus is to ensure a meticulous approach which is taken to gathering the necessary information required by the enquiry team,” said Read.

A report by the Canterbury Earthquakes Royal Commission of Inquiry detailed how the six-storey CTV building, which was designed in 1986 and completed around 1988, had a “design that was deficient in a number of important respects” and should never have been issued with a construction permit because it failed to comply with building regulations.

The commission also found the building was never properly structurally assessed after being damaged in strong earthquakes on Sept. 4 and Dec. 26, 2010, despite being inspected by three building officials.

Most of the 185 people killed in the 6.3-magnitude quake of February 2011 died in the building when it collapsed and caught fire.

The CTV victims included 64 Asian students studying at an English language school: 17 students from the Chinese mainland, 28 from Japan, 10 from the Philippines, six from Thailand, two from South Korea, and one from China’s Taiwan.

The New Zealand government bought the CTV site in July last year and plans to include it in a mainly residential area on the edge of the city’s new central business district. PNA/Xinhua