An office block that collapsed, killing 115 people, including 65 foreign students, in last year's Christchurch earthquake did not meet building standards, an official report found Thursday.

The six-storey Canterbury Television (CTV) building crumpled then burst into flames when a 6.3-magnitude quake hit New Zealand's second largest city on February 22 last year, killing those trapped inside the twisted wreckage.

The structure's failure accounted for almost two-thirds of the 185 fatalities in New Zealand's deadliest earthquake for 80 years.

An investigation by government-appointed inspectors found the office block did not meet the minimum earthquake building standards that applied when it was built in 1986.

Earthquake Recovery Minister Gerry Brownlee said the report had been passed on to police to see if further action was warranted.

"The report found there were three aspects of the design and construction of the CTV building that did not meet the standards of the day," Brownlee said.

"We note the report has now been passed onto the N.Z. Police to look into further."

Brownlee said the report "raises some serious questions about the structural integrity of the building".

"This news will be painful for the families, colleagues and friends of the 115 people who lost their lives in the collapse of the CTV building," he said.

The building housed the King's Education language school. Eight staff and 65 students, predominantly from China and Japan, died in the disaster that razed much of Christchurch's downtown area.

The building's disintegration and the subsequent inferno were so destructive that forensic specialists had to use DNA testing to identify the remains of many victims.

Separately, the national coroner's office announced the death toll from the quake had been raised to 185.

The coroner initially found 181 people were killed as a direct result of the 6.3-magnitude quake, but more deaths had been recorded as part of the toll in recent weeks after reviews of their cases, a spokesman for the coroner said.