Update 3.41pm: Waikato Police investigating this morning's fatal collision which closed a vital link between their district and the Port of Tauranga said initial indications suggest a tragic quirk of nature may have contributed to the crash.
District road policing manager, Inspector Freda Grace, said emergency services were still at the scene of this morning's crash near the intersection of SH2 and Rahu Rd in the Karangahake Gorge.
"The crash, which happened about 10.40am, is currently under investigation by the Waikato Serious Crash Unit and it's too early to confirm what caused the collision between an eastbound Holden Commodore sedan and a westbound Peugot car.
"What I can say however, is that we are looking into what part, if any, a large rock (similar in size to a medicine ball) found in the eastbound outside passing lane may have played in the crash.
It appears the man driving the Commodore may not have seen the boulder and struck it causing his car to career into the path of the Peugot."
Mrs Grace said the sole occupant of the Commodore died in the crash while a female front seat passenger in the Peugot suffered serious injuries and was airlifted to Waikato Hospital.
The male driver of the Peugot suffered minor injuries and initial indications are alcohol was not a factor in the crash.
"There is still a lot of work to go through before we can conclude what has occurred."
SH2 is expected to be closed for some time and this has placed a strain on other roads as SH2 is a key route through our district linking the Ports of Tauranga and Auckland and is used by high numbers of heavy vehicles.
"Traffic has been diverted north and south via SH2-SH27-SH24 and SH29 over the Kaimai Range for southbound traffic and the reverse route for northbound travellers.
"Drivers are advised to expect delays and exercise caution and patience while using this alternative route."
Mrs Grace said today's incident highlights the need for motorists to maintain their situational awareness at all times.
"Road safety is no accident. By having drivers and vehicles fit for the road we can hopefully work to prevent tragedies such as this morning's from occurring."
Earlier: Waikato Police are advising motorists travelling between Paeroa and the Bay of Plenty to expect delays as a fatal crash results in SH2, through the Karangahake Gorge, being closed this morning.
Sergeant Dave Raffan of the Waikato District Command Centre said emergency services were called to the scene of the crash on SH2 near the intersection with Rahu Rd about 10.40am.
"Some responders are still en route so we're unable to confirm all the details at this stage but initial information to hand is that one person has died following a collision between two cars in the gorge.
"We also understand two persons may be trapped but given the geographical location it may be some time before we can confirm this."
Mr Raffan said traffic management staff are en route to the area to establish diversions but motorists should expect considerable delay.
"At this point we would advise motorists travelling from the Thames Valley and Waikato heading towards the Bay of Plenty to consider using SH29 over the Kaimai Range."