One patient in serious condition was airlifted to Waikato Hospital.
Four other patients - three with minor injuries and one with moderate injuries - were treated at the scene.
Waka Kotahi New Zealand Transport Agency said on its Bay of Plenty Facebook page that Kopu-Hikuai Rd between SH26 and SH25 was closed but had since fully reopened.
SH25A KOPU TO HIKUAI - SERIOUS CRASH - 2:35PM A serious crash has CLOSED #SH25A (Kopu-Hikuai Rd) between #SH26 at Kopu and #SH25 in Hikuai. Please delay your journey or use an alternative route. Updates can be found here: https://t.co/WetUquGVIE. ^MF pic.twitter.com/39SfeJHYiL
— Waka Kotahi NZTA Waikato/BoP (@WakaKotahiWaiBP) July 15, 2021