Celebrity Cruises confirmed six passengers from the Celebrity Solstice ship were injured when a tour bus plunged 40 metres down a hill during a shore excursion in New Zealand.
All six were US citizens and two remain in hospital.
One is thought to be in a serious condition.
The bus veered off the road after hitting a car near Akaroa.
The car driver is also in a critical condition.
"Our thoughts are with all those involved and we are praying for their speedy recovery," Celebrity said, adding it had sent a care team to Christchurch to assist the injured guests.
In addition to the six receiving treatment, another 20 passengers were treated for minor injury and shock at the scene.
