The others killed included a 3-year-old boy, three women and one man.
The blast set off fresh calls for a crackdown on illegal fireworks that have become increasingly more common in Hawaii. Contraband explosives rock neighborhoods year-round but grow in frequency around the year-end holidays.
Police have so far arrested 10 people in connection with the explosion. Authorities accused them of reckless endangering, endangering the welfare of a minor and multiple fireworks offenses.
Police said they are working with prosecutors to file charges but it is taking time due to the number of people arrested, large volume of evidence being examined and fireworks being tested.
Authorities seized 500 pounds (227 kilograms) of unused fireworks from the scene.
Police said they expect to make more arrests.
Hawaii Gov. Josh Green has proposed allowing police to issue $300 tickets to those who shoot off fireworks and imposing potential class A felony charges and decades in prison on those whose use of fireworks leads to serious injury or death. The state Department of Law Enforcement has asked the Legislature for $5.2 million to hire eight people and expand a forensic lab to counter rampant fireworks smuggling.
Six of the injured were flown to a burn center in Arizona for treatment last month because Hawaii's only burn care facility reached capacity with the wounded from the incident. One of them, a 29-year-old man, died last week.