Cruise ship passengers were among the tourists on White Island on Monday when it erupted.

While no lawsuits have yet been filed, legal experts said they expected action in US courts by injured passengers and families of those who died.

There were 47 people on the island at the time. Eight have been officially declared dead and more than 20 are being treated for severe burns. The NZ military was carrying out an operation to recover eight other bodies still on the island.

Royal Caribbean ticket terms posted on its website spell out that the company is not liable for any injury, death or loss of property caused by an act of God, as well as war, terrorism or other events beyond the company's control.

Royal Caribbean will likely argue the disaster was an extraordinary event no one could reasonably foresee, said Robert Kritzman, an attorney with Baker Donelson in Miami.

"If a volcano were to erupt, clearly that isn't negligence on anyone's part, that's nature," said Kritzman, a former general counsel with Norwegian Cruise Line.

Royal Caribbean did not respond to questions about missing passengers or whether it told passengers of the risks of visiting the island.

"We grieve this tragic loss. We will to continue to offer our support and services to the families during this difficult time," the company said in an email.

Part of the case will turn on what the cruise line knew or should have known and what they told passengers about indications of increased volcanic activity.

"There are tremors, there are earthquakes and people monitor that," said Carlos Llinas Negret, an attorney with Nelson & Fraenkel who represents passengers.

"It all depends on what the cruise knew, and when they knew it."

Geological hazard tracker GeoNet raised the alert level for the White Island volcano in November and said on December 3 that "the volcano may be entering a period where eruptive activity is more likely than normal".

The cruise line described White Island as "one of the most active volcanoes in the world", according to a cached version of its website.

"Get close to the drama: Gas masks help you get near roaring steam vents, bubbling pits of mud, hot volcanic streams and the amazing lake of steaming acid," it promised.

The Virginia parents of one woman who was severely burned told a TV station that their daughter said she believed Royal Caribbean would not have let her visit the island if it were not safe.

The experts said in a typical shore excursion accident the cruise line tries to put blame on the third party that is hired to run the tour.

On its website, Royal Caribbean does not identify the company that ran the White Island excursion.

Passengers would have to show Royal Caribbean did not take proper care to vet the operator, lawyers said.

But lawsuits face the added challenge of overcoming the argument the eruption was unforeseeable.

Norwegian Cruise Line was able to fend off a class action lawsuit about a large "freak wave" hitting one of its ships in 2005 by arguing it was an unforeseeable event.

Regulators had concluded there was no wrongdoing by Norwegian.

Royal Caribbean is using the act of God defence against a class action about a powerful storm in 2016 that hit the ship Anthem of the Seas off the eastern United States.

Passengers said the company knew of the risks of the storm but tried to outrun it.

The dramatic description of the White Island tour on Royal Caribbean's website will likely be a focus of any lawsuit, with lawyers seizing on it to show the company knew a disaster was possible, legal experts said.

The company could argue passengers were fully informed of the dangers and received proper safety equipment.

"If they hand out gas masks that says automatically you know you have a risk," said Bob Parks, a Miami attorney who represents passengers.

Australian Associated Press