The fire seriously damaged three rowhouses and partially damaged a fourth in the 500 block of East Chestnut Street. At least 32 people have been displaced and were being assisted by the Red Cross, according to city officials.
The fire is under investigation but is not considered "suspicious," said Lentz.
Izquierdo and her son were among 15 people - 11 adults and four children from seven family groups - living in the dwelling, which was licensed for a single-family rental, city officials said.
The owner of the home, Willie D. Johnson, could not be reached for comment. He owns numerous properties in the city, according to public records.
Vara-Reyes and her husband, Refugio, who also lived in the home, were awakened just after midnight by the alarm. They smelled smoke.
The pair dressed quickly. Margaret Vara-Reyes gathered her 7-week-old daughter, Kelly, and grabbed a cellphone as Refugio banged on the door of the other third-floor resident, Ernesto Delgadillo Najera, 42.
Thick, black smoke billowed into the hallway, blocking escape to the floors below.
"We were running for our lives," said Margaret Vara-Reyes. "We decided to open the window by the roof."
Her husband grabbed a quilt to cover the baby. With the infant in her arms, Margaret Vara-Reyes climbed onto the roof. She called 911 and waited in the pouring rain for rescue.
The three adults debated whether to wait or to jump from the second-floor roof and risk serious injury. A 911 operator calmed her and assured her that rescue was imminent, said Margaret Vara-Reyes. Moments later, police and firefighters arrived.
A ladder was put up to the roof. At first, Margaret Vara-Reyes refused to go down without the baby in her arms. She argued with her husband.
He assured her it would be all right. She negotiated the ladder in her flip-flops, thankful he could use one arm to hold the baby while the other held the ladder, she said.
Once on the ground, they joined other residents for a head count. It was then that they realized that Elizabeth and Imanol, who lived in a second-floor bedroom, were missing.
Margaret Vara-Reyes ran to the back of the property to show police which bedroom the mother and son slept in.
"Flames were shooting out of every window," she said.
Soon, she and her daughter were taken by ambulance to Chester County Hospital so medical workers could evaluate the baby. It was there that she found out her two neighbors had perished in the blaze.
Outside the Red Cross shelter, wearing the clothes she escaped in and a donated purple sweatshirt, Margaret Vara-Reyes smoked a cigarette.
Izquierdo, she said, worked as a housekeeper at a local hotel. Imanol had just started school. They had no family in the area.
"She was very devoted to her son," said Margaret Vara-Reyes. The women met at nearby St. Cecilia's church.
Margaret Vara-Reyes recalled how the nurse named Diane made a home visit during her pregnancy and discovered her fire-alarm battery was missing. Diane went out and bought the battery.
"I want to thank her," Margaret Vara-Reyes said. "She saved our lives."
Contact Mari A. Schaefer
at 610-892-9149 or firstname.lastname@example.org, or follow on Twitter @MariSchaefer.