It was not yet known whether alcohol had played a part in the accident and police are awaiting the results of toxicology tests, Lynam said.
The woman driving the Suzuki Swift received serious injuries and was taken to Waikato Hospital where she is in critical condition.
The woman driving the Nissan suffered serious leg injuries and two other people were treated for minor to moderate injuries.
While the Waikato road toll was at two deaths, compared with seven deaths at the same time last year, death and serious injury was an avoidable tragedy, he said.
"We are urging drivers to be mindful of the fatal five: that is speed, alcohol, keeping left, seatbelts and reckless or dangerous driving, if everyone takes care to avoid involvement with each of these factors we will all be driving to survive and ensuring safer journeys for all road users."
- nzherald.co.nz