UPDATE: Body found after fatal explosion, fire at San Francisco Sunset District home

SAN FRANCISCO -- San Francisco fire crews using heavy equipment and cadaver dogs found the body of an unaccounted for resident at the Sunset District home destroyed by an explosion and fire Thursday morning.

The San Francisco Fire Department Public Information Officer tweeted out the sad news early Thursday evening.

UPDATE: New video shows moment Sunset District house exploded    

The adult victim was located within the building that burned by K-9 teams, fire officials said. More information on the victim including their identity will be provided by the San Francisco Medical Examiners' Office.  

A huge fire preceded by a large explosion injured two people including a firefighter and prompting the evacuation of surrounding homes.

RELATED: Suspect arrested in deadly explosion at San Francisco home

San Francisco Fire officials confirmed earlier Thursday that federal authorities from the DEA and ATF are also assisting in the investigation into the explosion that shattered windows up and down the 1700 block of 22nd Avenue.   

The fire burned a house on 22nd Avenue near Noriega Street and was initially reported at around 9:30 a.m. San Francisco Fire Captain Jonathan Baxter later told KPIX that fire dispatch received multiple calls at about 9:22 a.m. reporting an explosion at a home on the block.

Over 100 firefighters and 35 fire trucks responded to the fire, which initially prompted an evacuation order for the entire 1700 block of 22nd Avenue, though it was later changed to only an evacuation order for homes between the 1730 and 1750 block of the street. The remainder of the block was ordered to shelter in place.

The San Francisco Fire Department said the fire was upgraded to three alarms. A photo tweeted out by the SFFF Local 798 Union showed the residence fully engulfed in flames.

In a later photo tweeted out by the firefighters' union, the single-family home appeared completely destroyed with the roof and upper floor collapsed onto the lower garage area.

Baxter told KPIX that one person was found outside the home in serious condition after suffering burns and injuries. They were transported to a local hospital. He said windows in houses across the street had been shattered, "indicative of an explosion." A later update also confirmed that a firefighter suffered minor injuries during the incident but would be OK.

Baxter said all homes on the 1700 block of 22nd Ave. were being evacuated, but there was no threat to other homes in the area. A later tweet by the SFFD indicated that the evacuation of homes was narrowed to 1730-1750 on 22nd Avenue with the rest of the 1700 block of 22nd Avenue being advised to shelter in place.

"We were watching the news and all of a sudden, 'Boom!' The whole house shook," said neighbor Lou Samaris. "Contents of a cabinet came on the floor. So we jumped up. We thought something had run into our house."

Samaris was shaken by the blast and he lives on the next block over. In the house right next door to the explosion, Karen Lei was just sitting down for a conference call.

"I just heard a big boom and I was thrown out of my chair," Lei explained. "And obviously the glass was flying out of the windows. The front door was busted. As I was running out of the garage, I saw the fires coming."

Up and down the street, neighbors came out of their own rattled homes, trying to figure out what had happened.

"And I could just see what looks like a crumbled house," said Cessario Greenblatt. "It wasn't completely engulfed yet."

Moments later the house was consumed by fire, sending smoke towering over the neighborhood.

"Yeah, luckily fire, SF Fire Department was here pretty quick," said neighbor Will Choy. "Police here pretty quick."

"Yes, we have seen vehicles damaged, homes damaged," said SF Fire Chief Jeanine Nicholson. "And I think a lot of the neighbors here are just sort of in shock."

People from blocks away came to see the aftermath of the explosion they heard earlier in the morning. And many of the immediate neighbors are still waiting to get a better look at the state of their homes. Broken windows can be seen up and down the street, with many residents saying they think the damage goes far beyond that.

"My living room windows are blown out," said Jack Noriega. "My side door is jarred; we can't open that. Can't open the front door either."  

As of 12 p.m., the evacuation and advisory were lifted, Baxter said but residents who are away from their homes on that block are asked to stay away for now. Authorities said the explosion and fire destroyed the home at 1734 22nd Avenue and severely damaged the homes to the left and right of it.

KPIX reporter Jocelyn Moran was able to confirm that windows in houses and windshields of cars on the block were shattered by the reported explosion.

People living in the area reported hearing and feeling the explosion around the time the fire erupted.

Images from social media showed a large plume of smoke emanating from the fire. The fire department was urging people to avoid the area.

Firefighters alongside American Red Cross officials will continue to assist residents who were evacuated or displaced from the fire, according to Baxter. The number of residents displaced from the fire has not been determined.

There was no immediate word on the cause of the fire or the reported explosion. The investigation by fire officials and PG&E technicians is ongoing.

Wilson Walker contributed to this story.