One motorcyclist died on Friday and another is in a critical condition after they collided with oncoming cars near Puhoi.
Police believe the men were patched Black Power members travelling in convoy to a Northland tangi.
They are calling for anyone who saw a group of gang members on motorbikes riding erratically on State Highway 1 before 2pm on Friday.
The crash occurred when the two motorcycles - which were travelling on the wrong side of the road - collided with two oncoming cars near Schollum Access Rd.
Serious Crash Unit investigator senior constable Karl Bevin said one rider, a 54-year-old man from Stratford, died that afternoon from injuries he received in the crash.