Rescue teams searching for a missing bi-plane off the Coromandel coast have failed to find an oil slick possibly related to it.
Rescuers are concentrating on the coastline after sightings of the missing home-built aerobatic bi-plane, which disappeared shortly after take-off from Ardmore airfield on Tuesday morning.
Maritime New Zealand spokesperson Steve Rendle said an oil slick up to 30m long was spotted by one of the rescue helicopters involved in the search but a police launch failed to find it.
Mr Rendle said a police squad was doing a sonar search of an area 400m or so off the coast from New Chums Beach in Wainuiototo Bay.
The dive squad would investigate if the sonar picked up anything of interest to the search.
No distress beacon has been activated but a search was launched after a friend of the 53-year-old pilot reported concerns for his safety.
The plane is blue and white, with twin wings and an open cockpit.
The rescue team will evaluate its options overnight for continuing the search.