Christchurch police are closing in on those they believe are responsible for spraying graffiti at the site of the CTV building, where 115 people died in the February 2011 earthquake.
Police believe the site was tagged at night on Saturday, 3 August, along with several other central city locations. They have released security camera images.
Senior Sergeant Phil Dean says they were contacted by the owners of a cafe who believed they may have identified the taggers in their security camera footage.
He says three males walking around the central city between 11 and 11.30pm were identified.
Mr Dean says the vandalism is extremely distressing for the families of those who died and the wider community.