Mr Smith said the two girls in the back seats of the car, one aged 21 months and a 3-year-old, were freed and taken to Hawke's Bay Hospital.
He said the other driver, a female in her 30s, was also trapped in her car and received moderate injuries.
She, too, was taken to hospital. She was the only occupant of her car.
Police closed the stretch of road, near the intersection with Whakapirau Rd, for several hours as the Serious Crash Unit investigated.
A hospital spokeswoman said last night the two girls were in a stable condition, as was the other driver.
Police said the toddlers were being cared for by family.
Yesterday's death followed a series of fatal accidents on State Highway 50 near Maraekakaho in recent years.
In July 2012, a man was killed in a crash at the intersection of State Highway 50 and Whakapirau Rd.
That particular accident involved a van colliding with a ute, killing the van's passenger.
In August 2010, 63-year-old Albert Stone Renata died after his truck and trailer unit plunged down a bank while travelling east on SH50 near Maraekakaho.
A coroner later found Mr Renata was suffering from an underlying heart condition, which was likely to have caused the accident.
And in August 2003, 45-year-old Trevor Roy Hankin was killed when the truck he was driving hit a bank and rolled into a field along the state highway, north of the Maraekakaho monument.
Meanwhile, police continue their investigation into Saturday's fatal crash on the outskirts of Dannevirke.
Daniel Troy Leslie, 31, of Waipukurau, was killed after the car in which he was a passenger slammed into a power pole. Police say the vehicle was clocked at 124km/h in a 50km/h zone moments before the fatal accident.
The driver and a second passenger in the car were taken to Palmerston North Hospital and police said charges were likely for the driver.
