Updated 8.17pm: Four women have been injured, one critically, in a road crash in the lower Kaimai area in the Bay of Plenty this afternoon.

Emergency services were sent to the intersection of State Highway 29 and McLaren Falls Road about 3.20pm.

Initial reports said up to seven vehicles were involved, however emergency staff later said two vehicles had crashed.

St John ambulance staff say the injured women were in their early 20s.

One was flown to Waikato Hospital with critical injuries.

The others were taken by road to Tauranga Hospital.

The area was busier than usual today because the local Mclaren Falls Dam was opened for 'flow day' white water rafting and canoeing.