"I think at some stage one of the vehicles has gone onto the wrong side of the road," he said.
Sgt Kaio said one of the drivers was able to get out on his own was was taken to Waikato Hospital.
The second driver had to be extracted by local fire services before he was airlifted to hospital "with some reasonably serious injuries".
Sgt Kaio said the sheer nature of the hazardous material and any sparks or fire that may have eventuated from the crash could have made things more serious.
"So we were reasonably lucky," he said.
"For me I think it's about speed on our roads especially when they're as big as these vehicles are. It may well be that speed is one of the reasons why this particular crash occurred."
"I think the message to everyone is that speed does more damage the faster you go and today was a good illustration of that."