HONOLULU - UPDATE 5/21 6:14 P.M.

HFD Investigators have concluded their investigation and have determined that the fire was accidental.  

It was determined that the fire was accidentally caused by generator exhaust too close to stored combustibles in the garage.

Fire damages are estimated at $260,000 to the property and $80,000 to its contents. 

According to fire officials, the home did have working smoke alarms.

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UPDATE 9 P.M.

The Honolulu Fire Department provided the following update on the blaze that ripped through a Pauoa home Monday afternoon.

15 fire units equipped with 59 firefighters responded to the building fire on Pacific Heights Road.

The first unit arrived at 2:02 p.m. Monday to find a three-story single family home with the garage fully involved with fire. 

The fire was brought under control at 4:15 p.m. and the fire was extinguished at 6:23 p.m. Monday. 

HFD reports that an adult male was working in the lower floor of the home when he heard popping noises and then woke his brother who was sleeping at the time.

Both adults were able to escape the home without injuries.

Fire fighters overcame initial low pressure from the water supply in the area and building collapse of the entire garage and the right front corner of the home.

HECO was notified and responded to a downed power line that was a hazard to fire fighters.

The fire is currently under investigation and a cause has yet to be determined. Fire damage estimates are not available at this time. 

It is unknown if the home had working smoke alarms but it did not have fire sprinklers.

The Honolulu Fire Department says that it will continue to advocate for fire sprinklers in buildings. 

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UPDATE 6:38 P.M.

The building fire has been extinguished at 6:23 p.m. Monday, according to Honolulu Fire Department officials.

UPDATE 6 P.M.

Residents who live in the Pauoa area tell KITV4 that two men were inside the home when the fire broke out.

Part of the three-story structure collapsed from the fire. The fire has been declared under control, but fire crews are still trying to put out hot spots.

Hawaiian Electric Company was on scene because a power line came down, which made it more challenging for firefighters.

A neighbor who lives on the street below told KITV 4's Nicole Tam that he grabbed his hose and started shooting at the flames. 

"The heat was so tremendous. Even though I was standing 35-40 feet away the house burning. It felt like 250 degrees," neighbor Richard Oliver said.

"If there was a fire sprinkler in the single-family home, this fire wouldn't have gotten to that magnitude," Fire Captain Scot Seguirant said.

Two men were home when the fire started but they did get out safely.

Cause and damage estimates are still under investigation. 

UPDATE: 

The Red Cross is responding to the residents who lived at the home on Pacific Heights Road.

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UPDATE: 

The building fire on Pacific Heights Road has been upgraded to a 3-alarm fire with 15 units responding and 59 personnel.

Below photo courtesy of Steven Castillo:

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Reports of a building fire on Pacific Heights Rd. in Pauoa Valley.

First responders are heading to the scene.

This is a breaking story, more details to come as they surface.