Two patients in a serious condition and two in a moderate condition were all transported to Hawke’s Bay Hospital.
A helicopter also landed at the scene but wasn’t required for transportation.
Police said SH2 had closed between Stock Rd and Te Aute Trust Rd and diversions were in place.
“Motorists are advised to avoid the area and expect delays,” police said.
New Zealand Transport Agency Waka Kotahi said the Serious Crash Unit was on its way to the scene shortly before 5.30pm and advised motorists to “follow the directions by emergency services on-site”.
