UPDATED 5:50pm. One person has been killed and three people are critically injured following two separate car crashes near Thames.

A St John spokesperson confirms the motorist was killed in the crash on State Highway 25 near Orongo, south of Thames, which also left one other person with critical injuries.

'Four vehicles attended the incident and treated two patients and transported to Waikato Hospital,” the statement reads.

It was the first of two crashes which occurred on SH25 within 30 minutes of each other.

Emergency services were notified of the second incident which involved a car crashing down a bank on the Kopu-Hikuai Road/SH25 at 1.40pm, leaving two people with critical injuries.

Crash one:

At approximately 1:25pm on State Highway 25, two cars collided head-on, both with one occupant in each car.

At this stage, Police understand the silver car travelling westbound crossed the centre-line colliding with a green car travelling eastbound.

The driver of the green car died shortly after the incident and the driver of the silver car remains in a critical condition.

Police express their sympathies to the families of those involved while the Serious Crash Unit investigate the cause.

Part of the investigation will involve working to establish exactly what caused one of the vehicles to cross the centre-line.

The road remains closed between Kopu Bridge and the turn off to Turua until further notice.

Crash two:

At approximately 1:40pm, a second crash on Kopu-Hikuai Road occurred after a car travelling westbound left the road and went over a bank.

Four people were in the vehicle.

One person in a critical condition and a second person in a serious condition have been taken to Waikato Hospital.

A third person has been taken to Thames Hospital in a moderate condition.

The fourth occupant has minor injuries.

Kopu-Hikuai Road has one lane open now, but Police urge motorists to avoid the area unless absolutely necessary.

According to the New Zealand transport Agency website, both sections of SH25 where the crashes occurred remain closed in both directions, with diversions in place.

At Orongo, SH25 is closed between the Kopu Bridge and Hauraki Road, with motorists being diverted down Hauraki Road, SH2 and SH26/Paeroa Kopu Road.

While further east, one lane of Kopu-Hikuai Road/SH25A is open with stop/go traffic management in place.

However, motorists are being advised to expect long delays in the area and should avoid unnecessary travel where and if possible.

EARLIER 2.29PM:

Three people have been critically injured in two seperate crashes near Thames.

A third person is in serious condition after a car has gone over a bank on Kopu-Hikuai Road.

The first crash happened on SH25, near Orongo Road.

"Two people are in a critical condition and will be transported to hospital via helicopter," says police.

"The road is closed between Kopu Bridge and the turn off to Turua until further notice."

The serious crash unit is investigating the crash.

The second crash was called into police around 1.40pm after a car went over a bank on Kopu-Hikuai Road, between Kirikiri Valley and Puketai Road.

"There are two people in a critical condition and one in a serious condition.

"The serious crash unit has been advised and will also be investigating this crash."

State Highway 25 is closed in both directions just west of Kopu Bridge following an accident. Detour in both directions via Paeroa, says the NZTA.

State Highway 25 is closed between Kopu Bridge and Hauraki Road, in both directions. NZ Transport Agency advises to allow an extra 40 minutes for the detour via Paeroa.

"If you're travelling to Thames and the Coromandel Peninsula from the west along SH25, take Hauraki Rd through Turua, then SH2 to Paeroa, then SH26 back up to Thames and the Kopu-Hikuai Rd (SH25A).

"Reverse this if you're travelling west in the direction of Auckland from the Coromandel Peninsula."

NZTA says the detour is in place until further notice.

Earlier:

Motorists are being advised to use an alternative route following a serious crash on State Highway 25, near Thames.

Emergency services have been called to a two-car, head-on crash near Orongo Road.

Due to the serious nature of the crash, the NZ Transport Agency says the road is closed in both directions between Kopu Bridge and Hauraki Road.

'Motorists are advised to use an alternative route or delay their journey.”

SunLive will bring you more information soon.

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