Fire investigators determined today that a child playing with a lighter started the fire that caused an explosion in Palolo Homes on Tuesday, sending three people to the hospital.

In addition, damage from the fire and explosion was estimated at more than $1 million, said Honolulu Fire Capt. Scot Seguirant. Units B, C, and D of building 27 sustained more than $1 million in damage, while Units B, C, and D of building 25 sustained $15,000 in damage.

The fire began at about 12:30 p.m. in the second-story bedroom in Unit C of Building 27. About 45 firefighters arrived and found light smoke coming from multiple windows and debris on the lawn, showing signs of an explosion.

Four people were home when the fire started — a man, a woman, a boy and a girl — and were alerted to the fire by the odor of smoke, Seguirant said. The family was able to escape, he said.

Firefighters extinguished the fire at 12:52 p.m. Firefighters wrapped up an investigation into the cause today and determined the fire led to the explosion of a 3,500-liter oxygen cylinder, Sequirant said.

Earlier today, an MD Restoration crew cleared debris from the residential building and the surrounding area.

Dave Nakamura, executive director of the Mutual Housing Association of Hawaii, which owns the housing complex, said an oxygen tank was inside the unit for medical purposes.

The 61-year-old property manager of the 302-unit public housing complex sustained first- and-second-degree burns to about 30 percent of his upper body. Emergency Medical Services treated and transported him to a hospital in critical condition.

Paramedics also treated the resident services manager, 58, who sustained second-degree burns to about 25 percent of her upper body. She was transported to a hospital in serious condition.

A 70-year-old man with a history of a medical condition was also taken in stable condition to a hospital for possible smoke inhalation.

Seguirant said there were no other injuries reported.

Structural engineers are expected to inspect several apartments that were damaged in the explosion today or Thursday. Meanwhile, housing officials are working to relocate six displaced families to vacant units at the complex.

Seguirant said in a statement that two factors increase the chance of children playing with matches or lighters: children being unsupervised and children having access to matches or lighters.

“Securing matches and lighters away from children and being within view of the child greatly reduces opportunities for unwanted fire,” he said.