South Canterbury police believe that three people who were seriously injured in Ashburton on Sunday were injured in an altercation.
Officers found two injured people in a car on William Street at about 2am on Sunday, after attending a separate job on the same street.
They were taken to hospital by police and a third person, also seriously injured, took themselves to hospital.
Police said it appeared the three knew each other and no one else was being sought.
Officers were still trying to piece together what had happened.