Police investigating the 2011 collapse of the Canterbury Television (CTV) building which killed more than 100 people have executed four search warrants.
Documents and items of interest were seized, Detective Superintendent Peter Read said.
It is believed police removed items from the offices of Engenium Consulting Engineers, the new name for Alan Reay Consultants.
The CTV building was designed by Alan Reay Consultants and Reay was the principal. Reay ceased to be a director of the renamed company in September 2013.
Last September, police announced they were launching a criminal investigation after assessing information regarding the building's collapse during the February 2011 earthquake.
Engineering consultants Beca had been engaged to provide police with expert opinion during the investigation.
Police were seen removing boxes of files from the company's Madras St offices on Sunday and loading them into a van, Fairfax reported.
In 2012, the 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 115 people killed in the collapse called for legal action to be taken against those responsible.
The commission said Reay should have recognised that his employee David Harding was working beyond his limits when designing the building in 1986.
CTV Building
•Canterbury Television building collapses during February 2011 earthquake, killing 115 people.
•The building was designed by Alan Reay Consultants and Reay was the principal.
•A royal commission of inquiry found Reay should have recognised his employee David Harding was working beyond his limits when designing it