A three-year-old boy has become the fourth person to die after a massive explosion of fireworks at a home in Honolulu, Hawai’i on New Year’s Eve, according to a US burns doctor.

The blast killed three women and injured more than 20 people, with many suffering from burns to most of their bodies.

The US military flew six of the injured people from Honolulu to Phoenix, Arizona for treatment on Saturday because Hawaii’s lone burns centre doesn’t have the capacity to care for all of the victims.

The incident has since sparked renewed calls from Hawaii’s leaders to crack down on the state’s vast illegal fireworks trade by introducing enhanced enforcement and bigger penalties.

Kevin Foster, the director of the Arizona Burn Center, said in a press conference on Monday local time that the six victims flown to Arizona were aged in their 20s or 30s and were suffering from extensive burns.

“The smallest [injury] is about 45 per cent of total body surface area, almost half of the body burned, and the largest is just under 80 per cent of the body surface,” Dr Foster said.

He said many required emergency surgery before they could be flown from Hawai’i.

In addition to the burns, almost all of the victims are suffering “projectile injuries” caused by explosive particles that flew through the air, according to Dr Foster.

The doctor said all six patients were showing good vital signs, but they may not be able to resume a normal life for up to a year.

At least four of the patients are expected to remain intubated in medically induced comas for months, and some of them could suffer from post-traumatic stress disorder as a result of the incident.

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. 

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 explosive items. 

Video of the resulting explosion shows a rapid series of blasts shooting fireworks in the air and around the front of a house.

AP