A police spokesman told the Rotorua Daily Post in a statement police were still investigating but initial indications were the northbound car, driven by the man who died, possibly crossed the centreline and collided with two oncoming vehicles.
The injured woman was travelling in one of the other vehicles.
Police have appealed for witnesses to come forward, particularly anyone who knew the movements of the vehicles before the crash.
In particular, police wanted to speak with people who saw a silver Mazda Atenza travelling along State Highway 5 about 5am.
The spokesperson said at this stage police had not heard from any further witnesses since their first appeal for more to come forward.
Anyone with information could call 105 or visit 105.police.govt.nz and reference file number 240331/6189.
Kelly Makiha is a senior journalist who has reported for the Rotorua Daily Post for more than 25 years, covering mainly police, court, human interest and social issues.