Wednesday's accident occurred outside a home, the Honolulu Fire Department said.
The neighbourhood is near Honolulu's international airport and a joint US Air Force and Navy base and a little more than three kilometres east of the USS Arizona Memorial, which honours sailors who died in the attack on Pearl Harbour that drew the US into World War II.
The accident occurred just before outside a home in a Honolulu neighbourhood. (AP PHOTO)
Two people were declared dead at the scene, and the other 20 victims were taken to hospitals, according to Honolulu Emergency Medical Services.
"I've been in EMS over 30 years and this is probably one of the worst calls I've ever been on as far as the immense tragedy and amount of patients and severity of the injuries," Honolulu Emergency Services Department director Dr Jim Ireland said.
A statement from Honolulu mayor Rick Blangiardi put the death toll at three and said more than 20 people were injured critically.
"This incident is a painful reminder of the danger of illegal fireworks, which put lives at risk, drain our first responder resources, and disrupt our communities," Blangiardi said.
Several social media posts overnight showed video of fireworks being set off over a wide swathe of the city. Officials reported four other serious fireworks injuries unrelated to the blast.
The fire department said it was investigating the cause of the blast and had no details about how the accident occurred. It said there was no fire at the home.
26°C