At least four people are dead, one person was critically injured after an explosion at a bunker holding fireworks at the Waikele Business Center, the Honolulu Fire Department said.

The explosion happened about 9 a.m.

Witnesses told KITV4 people who were injured were lying down and had serious injuries, the witnesses said.

The victims were all Donaldson Enterprises Inc. employees and they were all men in their 20s, officials said.

The company housed illegal fireworks collected by authorities.

A Donaldson Enterprises Inc. spokeswoman says they are investigating what happened. Right now, they are focusing on the victims and their families, she said.

Honolulu Fire Department Capt. Terry Seelig said firefighters arrived to explosions at the bunker. They grabbed two people who were at the front of the bunker, he said. Those two were dead, Seelig said. There were two other people already outside, he said.

The critically injured patient was taken to Straub Clinic and Hospital with burns to 100 percent of the victim's body, sources said. Another person suffered minor injures in the blast and refused treatment, sources said.

There are several old World War II bunkers at the Waikele Business Center. The landlord, Peter Savio, said the explosion happened in one of the bunkers where fireworks were stored.

"We have a cave where fireworks were stored. It exploded. There are some fatalities. There are some injuries," Savio said. "Luckily for us it happened here at the caves, where it is sort of designed to handle these sorts of thing rather than a warehouse in town or a building in town. It could have been a lot worse."