Sniffer dogs were used to check predator-free islands off Northland's coast after a boat broke a mooring and drifted onto rocks, sparking a conservation scare.
A 6.5m boat, formerly used as a commercial crayfishing vessel, drifted from Flat Island near Great Barrier Island and beached in Boulder Bay on Whatupuke Island - in the Hen and Chicken Islands.
Department of Conservation ranger Marie Jordan said there were concerns there may have been rats on the boat that might have survived the journey and got onto the island.
The islands are a no-go zone without a department permit.
DoC officials went to the island last Thursday to help the owner, who had tracked down his boat.
Ms Jordan said two dogs trained to sniff out rodents were used to check three islands in the chain. Traps were also checked and they showed no sign of unwanted animals.
Ranger Neil Forrester said he helped pick up parts of the boat that were strewn across the small bay. The bottom of the boat had been ripped out.
The owner reported all the electrical gear and radio had been stripped, raising concerns people had landed on the island without permission.
Buoys used on commercial mussel farms were tied onto the boat wreck and when the tide came in it was partially floated and the owner towed it away.