Standing before the charred, burned-out house where four members of a West Philadelphia family lost their lives this week, Mayor Nutter implored city residents on Tuesday to make fire safety a top priority.

Get smoke detectors, Nutter said. Check the batteries. Devise an escape plan for family members in the event of fire, and practice it.

"In 2012, in the 21st century, in Philadelphia, no one should unnecessarily lose their life in a fire," Nutter said. "These are preventable tragedies."

A 4-year-old girl and her great-grandmother also died Sunday in North Philadelphia, less than a week after two firefighters died in a five-alarm blaze at a former factory site in Kensington.

The house on the 5200 block of Chancellor Street was boarded up Tuesday as Nutter spoke, a memorial of stuffed animals and toys growing on the steps. The house belonged to Seneca "Chuck" McClendon, 75, who was a cornerstone of the block and lived there with his son, Anthony McClendon; Rishya Jenkins, 23, Anthony McClendon's fiancee; and their children, 4-year-old Cyncere and 2-year-old Jayden McClendon.

Anthony McClendon was returning home from work in the predawn hours Monday when a fire tore through the downstairs of the two-story house, trapping his family upstairs. Chuck McClendon, Jenkins, and the children all lost their lives. Firefighters later found no working smoke detectors in the house.

Fire Commissioner Lloyd Ayers said that the blaze remained under investigation but that initial signs suggested it was electrical.

Relatives and neighbors on the close-knit block have been grief-stricken. During Tuesday's news conference, Anthony McClendon's mother collapsed in sobs, unable to stand or speak.

"We've all known each other for years," said neighbor Dawn Jones. "If one of us hurts, we're all hurting."

Nutter urged anyone without smoke detectors to call 311. Fire Department personnel will provide free detectors and install them, he said.

"They only work if you have one," Nutter said. "They only work if they have batteries. It only works if you check it. If it has no battery, it's just a piece of plastic."