Ruapehu Alpine Lifts (RAL) Ltd has voluntarily suspended its bus fleet after an urgent audit carried out by NZ Transport Agency.

The company says it was now sourcing its own transport to continue to ferry skiers up the mountain.

The company's fleet was subjected to assessment after one of its buses crashed with 31 passengers on board, killing one and injuring 18.

Hannah Francis, 11, of Auckland died in the crash while others were left suffering a variety of injuries.

NZ Transport Agency Director Transport Access and Delivery Robert Brodnax says RAL Ltd has voluntarily suspended their bus operations following the vehicle inspections carried out yesterday.

Independent of the police-led investigation of Saturday's crash, the NZ Transport Agency is carrying out an investigation of RAL's transport operations, which includes a full review of the company's Transport Service Licence (TSL).

No further comment can be provided on the inspections or on Saturday's crash while the police investigation, which is being assisted by the NZ Transport Agency, is ongoing.

Meanwhile, the company's chief executive Ross Copland is urging passengers involved in the crash to make contact with police.

"Our priority this week has been connecting with everyone on that bus, however privacy restrictions have made this a challenge. We would like to ensure that passengers are on the road to recovery, well supported and also keep them updated with the investigation that's underway," he said.

While the investigation continued, RAL has elected to outsource its transport and suspend its own transport service.

Contractors had been engaged to ensure continuity of services to transport visitors to the ski areas during the height of the ski season, he said.