Police are seeking video of rescue efforts at the Canterbury Television building in which 115 people were killed when it collapsed in Christchurch's February 22 earthquake.
They want the footage to aid their investigation of claims by families of some victims that not enough was done to rescue some of those trapped alive in the rubble who later died.
Well over half the 182 people killed in the quake were in the CTV building.
One of them, mother-of-two Tamara Cvetanov, spoke by cellphone to her husband, Srecko, on and off for almost three hours while trapped. Mr Cvetanov wants to know why she could not have been rescued in that time.
Detective Inspector David Long told the Herald police were seeking video images of the search and rescue phase after the building collapsed.
Officers were duty-bound to investigate issues that "may or may not have contributed" to quake deaths and were approaching the question with an open mind, Mr Long said.
There was clearly a period when people were trapped after the building collapsed, and some victims' families had raised questions about why they were not rescued.
Mr Cvetanov's lawyer, Nigel Hampton, QC, said his client wanted an independent review or ministerial inquiry at which he could argue that there was a period of inaction after the collapse and "a series of rather inept actions" that played a part in his wife's death.