Police have provided more details following the collision yesterday (26th July) morning on the A338, just north of Downton.
At around 7.30 am, a Vauxhall Astra was travelling southbound on the A338 between Charlton-All-Saints and Downton.
It collided with a Ford Transit coming in the opposite direction and then continued along the road, colliding with a Toyota Corolla.
The driver of the Vauxhall, a woman in her 20s, suffered serious injuries, and a child passenger in the rear of the vehicle suffered life-threatening injuries.
Another child passenger sustained minor injuries.
The driver of the Toyota also suffered serious injuries.
The driver of the Ford suffered no reported injuries.
Dorset & Wiltshire Fire and Rescue Service also confirmed that one person needed to be cut from a vehicle.
Police are appealing for help and asking for any witnesses to come forward with information to help the team investigating.
A police spokesperson said, "Any witnesses to the collision or anyone who may have dash cam footage is asked to contact the Serious Collision Investigation Team on 01225 694597, quoting log number 41 of today’s date.
"Alternatively, they can contact the team directly at SCIT@wiltshire.police.uk."

Salisbury Hosepipe Ban Starts Tonight
New community-backed scheme to improve pedestrian safety in Enford
Changes to parking charges in Wiltshire Council car parks to begin on 1 September
International GB Event Rider Opens Yard for Special Open Day
Mayor of Wilton Selects Salisbury Hospice Charity for Mayor's Appeal
Salisbury Searching for CCTV Volunteers
Residents Report Strong Smell of Smoke Over Salisbury
PCC calls for balanced approach to police reform
