A police spokesman told the Herald last night that the woman and baby were believed to be pedestrians and the baby had "grazes and a hit to the head".
There was also a report of a female in the car with an injured leg.
Numerous people called 111 to report the incident to emergency services, police said.
How to get help
If you're in danger NOW:
• Phone the police on 111 or ask neighbours of friends to ring for you
• Run outside and head for where there are other people
• Scream for help so that your neighbours can hear you
• Take the children with you
• Don't stop to get anything else
• If you are being abused, remember it's not your fault. Violence is never okay
Where to go for help or more information:
• Women's Refuge: Free national crisisline operates 24/7 - 0800 REFUGE or 0800 733 843 www.womensrefuge.org.nz
• Shine, free national helpline 9am- 11pm every day - 0508 744 633 www.2shine.org.nz
• It's Not Ok: Information line 0800 456 450 www.areyouok.org.nz
• Shakti: Providing specialist cultural services for African, Asian and Middle Eastern women and their children. Crisisline 24/7 0800 742 584
• Ministry of Justice: www.justice.govt.nz/family-justice/domestic-violence
• National Network of Stopping Violence: www.nnsvs.org.nz
• White Ribbon: Aiming to eliminate men's violence towards women, focusing this year on sexual violence and the issue of consent. www.whiteribbon.org.nz