The other, from Tikokino, had upper-body injuries.
"Four [occupants] were very lucky and didn't require ambulance transport - two were in a serious condition," Mr Hutchinson said.
He said the steep hill was in a remote area of farmland, which ambulance crews had to access with farm vehicles.
A hospital spokeswoman said yesterday one of the men had been discharged, while the other was in a stable condition.
The remaining injured occupants of the ute were treated at the scene.
Two ambulances from Waipukurau attended the incident, along with two crews from the Waipukurau Volunteer Fire Brigade, which had been at a day-long first aid refresher course at their station when the alarm was raised.
Brigade spokesman Owen Spotswood, a volunteer fireman for more than 50 years, said that while the weather was fine the terrain meant the ambulances, fire rescue vehicle and appliance were unable to reach the crashed utility or the injured men.
It was understood some of the men had been on the rear of the utility and were thrown clear as the vehicle began to slide on the slippery hillside.
Mr Spotswood said he didn't know how many times the vehicle had rolled, but it was near the bottom of the hill when it struck a tree.
Hawke's Bay's duck shooting season officially opened on Saturday.
During its return to Palmerston North the rescue helicopter crew was also dispatched to Rugby Park in Dannevirke, where a 19-year-old man from Palmerston North had suffered a badly broken leg in a Colts rugby team game against Massey.
The game was momentarily delayed while the helicopter was guided into the centre of the ground by local fire brigade members.
The man was airlifted to Palmerston North Hospital in a stable condition.
In response to the incident, police Senior Sergeant Greg Brown called on the public to be more careful when travelling on unfamiliar roads, be aware of the effects of fatigue after an early start, and avoid drinking alcohol until everyone was safely home.
"People can enjoy the start of the [duck shooting] season by being safe and getting home safe."