(AP) — A 3-year-old boy who died Monday was the fourth person to succumb to injuries from a massive explosion of fireworks on New Year’s Eve at a Honolulu home, and a doctor said six others faced long recoveries in Arizona where they were sent to be treated for severe burns.

The blast killed three women and injured more than 20 people, many of whom have burns over most of their bodies.

The U.S. military flew six of the injured to Phoenix for treatment on Saturday because Hawaii’s lone burn center doesn’t have enough capacity to care for all the victims.

Hawaii’s leaders have intensified their oft-repeated calls to crack down on the state’s vast illegal fireworks trade with stepped-up enforcement and greater penalties.

The six taken to Arizona are all in their 20s or 30s and have extensive burns, Dr. Kevin Foster, the director of the Arizona Burn Center, said at a news conference streamed online.

The person with the least has burns over 45% of their body. The patient with the most has burns over nearly 80% of their body. Each of the six is using a breathing tube and most are in medically induced comas.

It will be six months to a year before any of the victims are able to return to anything resembling a normal life, Foster said. Four patients will likely have to remain intubated and in a coma for months, he said.

The patients will likely suffer post-traumatic stress disorder, Foster said, adding the burn center has two full-time psychologists and a psychiatrist hospital on staff to help them.

“There’s something uniquely and particularly horrifying about being burned, especially from this type of injury,” Foster said. “And we anticipate that all of these patients are going to have some adjustment issues.”

Many required emergency surgery before leaving Hawaii and a number had traumatic injuries in addition to burns, because of the explosions and resulting projectiles, he said.

Hawaii’s diverse population has long celebrated New Year’s with fireworks but in recent years professional grade aerial explosives have been growing in popularity even though they are illegal for amateurs. Neighborhoods across Oahu light up for hours as residents launch aerial fireworks into the sky from the narrow streets in front of their homes.

Honolulu authorities say a person attending a party lit a bundle of aerial fireworks, which fell on its side and shot explosives into two crates that contained additional aerials. Video of the resulting explosion shows a rapid series of blasts shooting fireworks in the air and around the front of a house.

One of the patients transported to Arizona has burns over 72% of his body, while another man and his girlfriend have burns over about two-thirds of their bodies, according to GoFundMe fundraisers posted to help pay for their medical care.