The Department of Conservation says firefighters who battled the blaze which badly damaged the Midland rail line had to compete with 80km/h winds and 30m-high flames.
The Rail and Maritime Union today questioned the firefighting effort, after the fierce scrub fire in the Canterbury hill country badly damaged bridges and knocked out the line to the West Coast for at least the next six weeks.
A total of 17,000 Tranz Alpine passengers booked to travel to Greymouth have had their bookings cancelled.
A Department of Conservation spokeswoman said protecting structures was the first priority of their firefighters. At one stage, the fire was under a rail viaduct and could not be reached.
"Everyone threw what they could at it."
They tried to put people on the ground but had to withdraw amid concerns for their safety. At the time the area was buffeted by 80km/h north-west winds and firefighters had to contend with 30m flames near the structures and in 30C heat.
Union general secretary Wayne Butson said KiwiRail jobs on the West Coast were secure, even though there were no trains for the duration of the closure as staff would be redeployed to help contractors repair the damaged infrastructure, between Cass and Springfield.
However, he was disappointed with the extent of firefighting at the weekend.
"I don't understand how helicopters with buckets and fire crews ignored valuable infrastructure," Butson said.
"I don't understand how it was allowed to sustain the damage. They don't allow houses to burn."
Butson said each rail viaduct on the Midland Line had a reservoir adjacent to it.
Kiwi Rail also had high capacity pumps at Springfield which were never utilised.
"They were not moved out of the sheds."
As a result of the fire, coal from the Stockton open-cast mine was being stockpiled at Ngakawau, and the Tranz Alpine tourist trains cancelled until at least April.
Butson said he thought the six weeks estimated by Kiwi Rail to reopen the line was "extremely optimistic".
Three days ago Kiwi Rail group manager Todd Moyle said it was "grateful to the New Zealand Fire Service and the Department of Conservation for their amazing work over the weekend to bring this 300ha fire under control".
- Greymouth Star