Divers will start searching the Kawarau River this morning for two soldiers believed to be in a military Unimog truck which plunged down a gorge into the river yesterday.

Police today named the missing soldiers as Shane Adrian Ohlen, 21, from Wellington, and David James Partington, 17, from Linton.

The body of a third soldier who was in the truck, Ashley Patrick Goodwin, 19, from Motueka, was recovered yesterday.

Police said the soldiers and the vehicle were taking part in an army driver training exercise when the Unimog crashed into the Kawarau River at the Roaring Meg power station in the Kawarau Gorge.

The defence force have said they will conduct an investigation into how the crash happened. It is the fourth fatal accident involving a defence force Unimog in the last five years.

Mr Goodwin and Private Ohlen were based at Burnham Military Camp, and Private Partington was based at Linton Army Camp.

Police believe the missing men's bodies are trapped in the Unimog, which is completely submerged in the rapid river.

Sergeant Steve Ereckson of Cromwell police said as well as a dive team searching the river, the police will also search the riverbanks for the missing men.

He said the speed of the river will make it difficult for the search party.

The focus will be to find the truck first, he said.

Mr Ereckson said the police will also look at why the crash happened.

"The truck, it appears, has ridden along the top of the barrier for quite a distance before coming to a stop straddling the barrier, and we are looking at reasons why it may have dropped down the bank."

He said the road was difficult to drive but speed, weather and road conditions did not appear to be factors in the crash.

Army spokeswoman Major Denise Mackay today defended the army's safety record

"This was a driver training exercise and what all of the young soldiers who were on this course were learning to do was to drive the Unimog truck.

"They all had their Class 1 licence and they were advancing to the next level, which was why they were practising open road driving in the Unimog."

It was the fourth week of a six-week training course.

"They'd been advancing through open road driving... once they'd achieved that they would have moved to the next level which meant slightly more complicated and challenging terrain," Maj Mackay told National Radio.

The stretch of State Highway 6 being driven yesterday was an open road, which was well travelled by many different types of vehicles, Maj Mackay said.

"It wasn't a remote area."

The army would undertake a full investigation.

"If there are some recommendations which come out of there that suggest that the army does need to reconsider where Unimog training takes place, that's something we will look at," she said.

In August last year, two soldiers lost their lives on Banks Peninsula when a Unimog left the road.

Private Sean James Dougherty, 29, and Private Daniel Kairua, 22, died when their truck rolled almost 400m off a road near Wainui on the peninsula.

A third soldier in the Unimog was badly injured in the crash, which happened in icy conditions.

The crash was the fifth fatal incident involving a defence force Unimog since 1994.

"(Yesterday) was certainly a different type of road...that (Banks Peninsula) inquiry has just concluded and there are a number of recommendations which will be released shortly," Maj Mackay said.

She said yesterday's accident had to be looked at in context.

Unimogs were all fitted with "protective structures", implemented after Staff Sergeant Billy White was killed in a crash in East Timor in April 2000.

"We've taken that precaution already, which I think is important.

"We need to be careful not to take any kneejerk reactions and make sure that any decisions are well considered."

Military police were making their way to Cromwell this morning to work on the crash investigation.

The current driver training course the soldiers were on near Queenstown would not be completed.

Maj Mackay said the army's first priority was to make sure soldiers involved in the accident, and others taking part in the training exercise, were well supported.

"They'll be travelling from Queenstown to Dunedin today, where they'll be meet by one of our army chaplains," she told National Radio.

Military liaison officers were with the three families involved, she said.