Fire engulfed a two-story row house, killing at least six people and injuring five others.
Some of the victims were burned so badly that firefighters were unable to determine their age or gender, said Fire Chief William Goodwin. He described it as "possibly be the worst scenario I've seen in my 32 years."
The fire was reported about 7:20 a.m. The first firefighters to arrive found both floors engulfed in flames. They were able to rescue three people, and three others managed to escape.
Of the victims who died, four were found in a second-floor bedroom, and one was at the base of the stairs, Goodwin said. Another died on the way to a hospital.
Goodwin said the heat from the fire was so intense that the victims died quickly.
"Something of this magnitude, you get one breath, that's it," he said. "You can't breathe the super-heated air. You can't breathe the toxins."
Fire officials said they believed the blaze started on the first floor of the home. The cause was under investigation.
Russian officials have repeatedly declared that Israeli aviation poses a threat to the Russian military in Syria.