(CNN) -- Seven people, including a toddler, died when fire roared through a three-story home in southwest Philadelphia, Pennsylvania, on Friday night, fire officials said.

Firefighters work to put out a fire at a town home Friday night in Philadelphia, Pennsylvania.

Six of the victims -- three adults, a teen and two children -- were found in the townhome's basement, huddled together, Philadelphia Fire Commissioner Lloyd Ayers said.

A 2-year-old boy who was pulled from the burning house by firefighters was later pronounced dead at Children's Hospital, Ayers said.

Eleven people, all of Liberian nationality, lived in the basement of the home, he said. Two were rescued by firefighters and two escaped on their own, Ayers said. Watch firefighters at work on the blaze »

There were no stairs from the basement to the upper level and there was only one door leading out, he said.

Early clues suggest a kerosene heater may have started the blaze, but the fire marshal has not officially determined a cause, Ayers said.

"We found serious issues in the house," he said.

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The home did not appear to be equipped with smoke detectors, the fire commissioner said.

"We have not found any smoke alarms at all, which we are very saddened by," Ayers said.

Wade Lee, who lived in the same building, said the landlord had helped tenants work out fire evacuation plans.

Lee said the victims often brought his family fresh vegetables from their garden, and the children were a joy.

"Our wishes are with them right now, more so than for ourselves," he said. "Just hearing the children laughing, and not being able to hear that no more is grievous to us all."

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