They said police remained at the scene for some time and were photographing the area, so they assumed it was serious.
Hato Hone St John was called to the crash at 1.17pm.
St John said it responded with one ambulance and one operations manager responded to the scene with one rapid response unit.
A helicopter was also en route, but not required.
“Our ambulance staff treated one patient and took them to Tauranga Hospital in a critical condition.”
Motorists are being advised to avoid the area and expect delays.