Electrical wiring caused the blaze that killed a family of four early Monday in West Philadelphia, fire officials announced this morning.

The blaze, which broke out just before 5 a.m. in a rowhouse on Chancellor Street near 52nd, killed Rishya Jenkins, 23, her stepson Cyncere McClendon, 4, her son Jayden McClendon, 2, and her soon-to-be father-in-law Seneca "Chuck" McClendon, 75. It was the city's third fatal fire in a week. Jenkins was planning to get married in June; her fiance discovered the fire and tried vainly to save his family. The elder McClendon, a retired postal worker, had lived on the block since the early 1980s.

"Non-permanent electrical wiring" was the official cause. That means wiring such as extension cords, Executive Chief Richard Davison said.

A fire on Sunday that killed a 4-year-old girl and her great grandmother in North Philadelphia was caused by unattended cooking, fire officials ruled. That fire, in a rowhouse on Firth Street near 13th, left Nevaeh Bryant, 4, and Ardalia Bumpus, 79, dead.