Police are investigating reported sightings of an 11-year-old and his estranged stepfather as far north as Auckland.
Mike Zhao-Beckenridge disappeared from Invercargill on 13 March with stepfather John Beckenridge, 64, in breach of a custody order.
More than six weeks after the pair went missing police say they are still treating the case as a missing persons investigation and up to nine officers at a time are working on it.
Sergeant Dave Kennelly of Invercargill police said reported sightings had come from the Otago-Southland area to the upper North Island.
A dive team is still waiting to recover John Beckenridge's car from where it has been located in the sea near Curio Bay in the Catlins. The bay is being pounded by up to five-metre swells.
Earlier, police had said evidence pointed to a murder-suicide.