Although the investigation is in its early stages, police believe both riders were knocked off their bikes.
Investigations are underway to determine the circumstances of the incident, said the spokesperson.
Ngapipito Rd is closed between Mangakahia Rd (SH15) and the intersection of Tana Rd, Moerewa.
The road is expected to remain closed for some time, and motorists are advised to avoid the area, they said.
Police urged anyone with information to contact them.