NZ First has accused KiwiRail's "incompetent management" of trying to hush up the derailment of a coal train on the West Coast.

The incident happened on Sunday afternoon north of Westport at Birchfield, on State Highway 67, when the wheels of seven of the train's wagons came off the rail.

No one was injured.

NZ First's transport spokesman Brendan Horan today said any derailment involving a coal train was "pretty serious".

"Quite clearly there is a lot of work that needs to be done on that rail link. KiwiRail had 'tried to hush it up'", he said, telling reporters they would have to ask the Corporation's "incompetent management" why.

"It's one of a series of bungles with that management team."

The Government was preparing to sell KiwiRail, Horan claimed.

The management would ensure it went to the "lowest bidder".

However, KiwiRail spokeswoman Jenny Austin denied it was trying to hush the derailment.

"You don't hide a derailment, especially when it's near a state highway. Goodness me, not at all."

It was too early to know what caused the wheels to come off the rail but KiwiRail would conduct an investigation into the incident, she said.

"It could be any number of things."

The wagons were still being recovered, Austin said. 

"Whenever wagons derail, we have to get a crane to lift them back onto the rail and these were fully loaded coal wagons. So we had to spend yesterday building an access ramp up to the track to get the crane in."

Four of the seven wagons had now been re-railed with the remainder expected to be completed by the end of today, she said.

KiwiRail would repair the track tomorrow and hoped to have the line open again on Thursday.

- © Fairfax NZ News