The owner of the tour bus company involved in a fiery crash near Te Anau says it appears the rental car crossed the centre line.
Two people in the car died when it and an Explorer Tourlines bus crashed on the Te Anau-Milford Highway on Tuesday afternoon.
The car was so badly damaged it took the police two days to confirm how many people were in the car.
Explorer Tourlines owner Stephen Cook held a news conference today in Christchurch.
He said he was horrified to hear two people died in the accident. He was trying to make sense of the tragedy.
Mr Cook said the 16 South Korean tourists on the bus suffered minor injuries, with the most serious being a fractured ankle.
All were shaken and had returned to Korea. The driver and the tour guide were traumatised.
While the cause of the crash was unclear, he said he understood the car crossed the centre line. He did not know what caused it to do that, he said.
Mr Cook said the Te Anau-Milford Highway was known as a risky road and some action needed to be taken to improve its safety.
The highway is the only road to Milford Sound. In peak season, thousands of people make the trip each day.
Tourist operators say the high number of tourist drivers, distracting scenery and alpine conditions made the road challenging.
Mr Cook said Explorer Tourlines was co-operating with the police inquiry into the crash. The bus driver was on special leave.
He thanked emergency services and members of the public who helped at the scene.
Mr Cook said he intended to get in touch with the two victims' families at a later date.
Police said they were still investigating the cause of the crash and would not "speculate".