Commuter services between Wairarapa and Wellington returned to normal today, three days after a landslide derailed a passenger train near Upper Hutt.

Workers spent the weekend battling poor access and a sea of mud to remove the train's damaged locomotive, which slammed into the slip as it left the Maymorn tunnel on Thursday night.

The derailment marooned the 300 passengers on board Thursday's train and forced the cancellation of all services until last night.

After carriages were cleared from the scene, the locomotive was re-railed yesterday afternoon and services resumed with the 6.50pm service from Wellington.

KiwiRail engineer Walter Rushbrook said the project to get the locomotive back on the rails was one of the most difficult he had faced.

Staff had to build about one kilometre of road, mainly by clearing scrub and pouring gravel, so two cranes could reach the site. They then had to build foundations so the cranes could lift the 85-tonne locomotive back on to the track.

"The road was difficult to make because there was so much water to contend with, but we came up with some cunning drainage systems and used a lot of pumps to make sure the area was clear of water," he told the Dominion Post.

Tranz Metro spokesman Nigel Parry said that, although heavy rain was believed to have caused the slip, an investigation would still be carried out as the slip came down just below Upper Hutt's Mt Marua housing subdivision.

- NZPA