Firefighters fear that at least one person has died in a fire burning in Oakland this morning, but the dangerous blaze kept them from immediately retrieving the body.

KRON 4 reports that the fire at 2551 San Pablo Avenue was reported at around 6 a.m. Monday. Initially announced by officials as a three-alarm fire, the blaze at the three-floor structure was swiftly upgraded to four.

According to ABC 7, as many as 60 people live in the building. While most evacuated without incident, firefighters said that they had to rescue seven. The Chron reports that three people suffered injuries due to smoke inhalation, and are in critical condition.

Addressing the media Monday morning, Oakland Fire Department Battalion Chief Eric Logan says that the fire caused the roof and floor to collapse, and firefighters were ordered out of the building, and had to "battle the flames from the ground and via extended ladders," NBC Bay Area reports.

But before they evacuated, they saw what they believed to be the body of a victim who had died in the fire.

“When firefighters first went in, they saw what might have looked like a body on the third floor, but the flames were so intense they had to retreat,” the Chron quotes Logan as saying. “We have to get more of this fire out to see.”

“They weren’t sure if they did see a body but as they were trying to make their way in, there was so much fire, that they weren’t able to make any more access,” KQED quotes Logan as saying.

CBS 5 reports that the building "housed people recovering from addiction." According to the Chron, "the first and second floors house a drug rehab center," but the third floor are apartments.

Resident Kirstin Evans tells NBC that "I just heard screaming and breaking glass, sounds of wood breaking and explosions...I looked at my window and it was all orange and yellow. I ran out of my apartment and it was all smoky and debris was all over the place."

Fantazhia LaTonda, who'd just moved into the building with her boyfriend, tells the Chron that the couple was trapped by the flames, and had to be pulled through the window by firefighters. I was scared. I thought I was going to die,” she said. “I was worried we weren't going to get out. Just burning. That's not the way I want to die. Burning,”

By 8 a.m., NBC reports that "crews appeared to be gain an upper hand in the fight" as "large clusters of flames were replaced by billowing plumes of white smoke."

Evans tells NBC that she believes the fire was "caused by a burning candle resting in a residence on the second floor of the building."

It's still unclear if the structure had sprinklers or smoke detectors. As quoted by KQED, OFD's Logan says that “The amount of smoke and fire that we had at the onset - a sprinkler system probably wouldn’t have been able to put out that amount of fire if they had a sprinkler system."

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