A Maritime NZ spokesperson said they received distress beacon alerts just after 2pm today from the Rangitata River and responded with their Rescue Coordination Centre (RCCNZ).
The spokesperson said they are aware of at least three people who are injured, including a head injury, spinal injury and broken leg.
The exact number of jet boats involved is still unclear.
Four helicopters were scrambled to provide help, two from RCCNZ and another privately owned helicopter from Christchurch. Additional helicopters are en route from Greymouth and Christchurch.
By Rachel Maher