Some of the volcano victims have burns covering up to 90% of their bodies.

New Zealand doctors need an estimated 1.2 million square centimeters of skin grafts to continue treating burn victims from Monday’s volcano eruption, officials said.

Dr. Peter Watson, chief medical officer of the Counties Manukau District Health Board, told reporters that 29 patients suffering burns over at least 30% of their bodies were still receiving treatment at hospitals across New Zealand since the volcano erupted on White Island. Twenty-two of the patients remain on airway support due to the severity of their burns and other injuries. Some have burns covering as much as 90 percent of their bodies, according to Watson.

“The majority [of patients] are very severe,” Watson told a press conference Wednesday. “Our surgical teams have been working around the clock.”

Watson said the nature of the burns is complicated by the gases and chemicals from the volcanic eruption, requiring more rapid surgical treatment than would be the case for thermal-only burns.

An order has been placed with the United States for the additional skin as well as more wound dressings, according to Watson. The skin is the largest organ of the human body, with a total surface area of about 22 square feet.

A total of 47 people, including at least nine Americans, were visiting White Island, also known as Whakaari, when the volcano suddenly spewed steam, ash and debris into the air on Monday afternoon. Thirty-four people were rescued via helicopters on Monday and taken to hospitals for injuries, while others were stranded on the volcanic island, according to the New Zealand Police, which said there are likely no survivors.

At least six people have died since being rescued, police said.

Authorities are working to confirm the identities of the deceased as well as the injured. The New Zealand Police has launched an investigation into the circumstances of the deaths and injuries on White Island.

Police on Wednesday released the names and nationalities of another nine people who are listed officially as missing. Seven are from Australia and the other two are New Zealanders.

Earlier, police said eight people who are missing were believed to be still on the island and presumed dead.

Rescue workers have been unable to return to the island to recover the bodies of those believed to be killed because the conditions are too dangerous and unpredictable. A 5-mile no-fly zone is in place around the island, along with a 5-nautical-mile maritime exclusion zone.

“The environment on the island has changed, with increased volcanic activity since early this morning,” New Zealand Police Deputy Commissioner John Tims said in a statement Wednesday. “We are standing by and ready to go as soon as we can be confident that the risks on the island are manageable.”

White Island, located 30 miles offshore from mainland New Zealand, is home to the country’s most active cone volcano. The uninhabited island has had regular eruptions for years but has become a widely popular tourist destination, accessible only by boat and helicopter.

The family that owns the island has asked that the public respect a new prohibition restricting access to the ash-covered site.

Those who cannot get in touch with a friend or family member in the wake of the volcanic eruptions are urged to register them by visiting the New Zealand Red Cross website or call the New Zealand Police.

ABC News’ Alexandra Faul, Marcus Moore, Kirit Radia, Christine Theodorou, Anna Thomas, Alondra Valle and Karson Yiu contributed to this report.