A 39 year-old male driver and male passenger aged 23 were taken to Dunedin Hospital by helicopter.
The driver had a fractured skull and was in a serious but stable condition.
The passenger was critically injured.
The other two men, aged 38 and 22, were taken to Timaru Hospital by ambulance with moderate injuries.
An investigation into the crash is ongoing but police told the Herald yesterday that speed and alcohol were thought to be factors - and the Toyota's occupants did not appear to be wearing seatbelts.
One of the men, the driver of the 1988 Toyota, is a local and worked as a shepherd.
The other moved to Kurow a few weeks ago from Britain to play rugby for the club.
He was understood to be on life support last night as his family frantically travelled from overseas to be with him.
A source close to the club said everyone was in shock. "I know the people that were involved. They are pretty good mates of mine," he said.
"It's a big shock, we're a really close community. The driver is a great fellow, he's well respected. He is a fantastic leader within the rugby team and I have a lot of respect for him. The other guy has just come out from the UK. It's quite terrible for his family."
He said the others in the car had injuries that were not life-threatening.
After playing a club game on Saturday, the group are understood to have been socialising at a party or function in the area. They were heading home with their four mates when the crash happened.
Other friends were following the Toyota in another vehicle and called 111 after seeing it leave the road.
It is understood that local emergency-service personnel will be given support after attending the incident.
"Apparently it was chaos," Senior Sergeant Mike Brooklands said.
Kurow Rugby Club president and premier team manager Mike Paton said it was too early to comment, but a post on the club's Facebook page said: "Our thoughts and prayers go out those involved in the accident up the Haka [Hakataramea Valley] and to their friends and family."
Sergeant Mike van der Heyden of Waimate police said it was too soon to say what caused the crash but speed, alcohol and unworn seatbelts were factors being investigated.
"We are looking at all possible causes...the investigation is ongoing and we are waiting on the results of blood tests."
He said some relatives of the injured were still being contacted.
Kurow is where All Black captain Richie McCaw was raised and first played rugby. In recent years, the club has had a string of imported players from the United Kingdom, Pacific and South Africa.
-Additional reporting NZME. News Service
