Three children and a man were killed early Sunday morning in a raging house fire in North Philadelphia, where authorities said they had not found any functioning smoke detectors.

The children’s mother escaped the flames through a window.

Heavy fire was visible from both floors of the two-story rowhouse on the 3200 block of Hartville Street in the city’s Kensington section when firefighters arrived shortly after 2 a.m., hampering their access, Fire Commissioner Adam Thiel said.

“For us, the worst possible thing is to not to be able to save a life in an incident like this, or so many others that we’ve had this year, and in prior years,” Thiel said at a news conference Sunday at the site. " ... We are frustrated, and we are mourning. We are mourning with this community, with these families.”

Thiel said the mother was hospitalized in stable condition and expected to be released.

The cause of the fire was under investigation by the Fire Marshal’s Office.

According to public records, the property has been owned by Edwin and Gloria Ruiz since 2004.

Reached by phone Sunday afternoon, Edwin Ruiz said the tenants were Alexis Rios and Jasmin Santana Vega, whose first name is spelled Yasmin in some public records. The couple moved in about 2014 and had a rent-to-own arrangement, according to Ruiz.

Ruiz, who lives in Ardmore, said that there were smoke detectors in the Hartville Street home when he last visited, but that he had not been inside since the family started renting. Since then, Ruiz said, the family had renovated the interior of the home.

Philadelphia Department of Licenses and Inspections records do not show an active rental license on the property, something Ruiz acknowledged Sunday. An L&I spokesperson could not immediately be reached on whether a rent-to-own arrangement eliminates the need for a rental license.

Next-door neighbor Levi Walker was awakened by the smell of smoke about 2 a.m. He said he made sure it wasn’t his own home on fire before going outside to see the first-floor air conditioner ablaze and falling out of the window of 3239 Hartville. Then he saw a woman fall on the ground and then run to a nearby truck, screaming something in Spanish that he did not understand.

Flames initially engulfed the first floor, he said, before shooting upstairs. After alerting neighbors and calling 911, Walker, who is new to the neighborhood, wanted to help but realized that the fire was already too far out of control, he said

“I didn’t think it would be that much fire that fast,” Walker said.

The first fire truck arrived “exactly two minutes” after the 911 call came in, but due to the flames coming from the rowhouse, the vehicle could not pull fully in front of the structure, Thiel said. Not all apparatus could get down the narrow street with cars parked along one side, he said.

“We were able to put hands on one of the juveniles inside; unfortunately it was too late,” Thiel said.

One neighbor said several minutes passed before crews could begin extinguishing the flames. Department spokesperson Kathy Matheson said the firefighting response will be part of the investigation.

The investigation so far has yielded one troubling absence, Thiel said: “We have not found any evidence so far of working smoke detectors in this home.”

» READ MORE: How many smoke detectors should you have and where should you put them?

Thiel said 21 people have died in fires in Philadelphia this year. In January, the city experienced its deadliest in a generation when 12 people, including nine children, were killed in a rowhouse fire in Fairmount. More than 20 people were recorded living in that Philadelphia Housing Authority duplex and there were no working smoke detectors in the unit. Officials concluded that the blaze had very likely been started by a surviving child who was playing with a lighter near a Christmas tree.

» READ MORE: Philly fire commissioner after Fairmount blaze: ‘Root cause’ is lack of access to safe, affordable housing

On Hartville Street, Jose Salas, who lives two houses down from the scene of the fire, remembered Rios as a hardworking mechanic who had fixed up the house.

“He’s a good guy,” Salas said. “He don’t bother nobody.”

He said the last time he saw the children, they were riding their bicycles.

The school district identified the children as Alexangel Arroyo-Santana, a sixth grader at John B. Stetson Charter School; Yadriel Arroyo-Santana, a third grader at Lewis Elkin Elementary School; and Yamalier Arroyo-Santana, who was in kindergarten at Elkin.

A GoFundMe has been established by the Elkin school community “to help the mom of Elkin students that perished in a fire on 4/24/22.” As of 7 p.m., the $5,000 goal had been surpassed.

“They are our babies,” an emotional Charlotte Maddox, Elkin’s principal, said at the Thiel news briefing Sunday afternoon, joined by teachers from the school.

Owner Ruiz said he has insurance on the property, but is “not going to touch a penny.” Instead, Ruiz said, he will “get the money to [Vega].”

The fire was brought under control at 2:28 a.m., according to fire officials. By late Sunday morning, every window and the front door on the gray, painted-brick home were gone. Black char marks ran from the first-floor window up the front of the house to the second floor. Windowsills were blackened. A bench and some drawers lay on the sidewalk; damaged shoes and clothes peeked out from a pile of ash and debris.

The causes of the deaths will be determined by the Medical Examiner’s Office, authorities said.

More than 60 firefighters, medics, chiefs and support personnel responded to the fire.

Newsroom researcher Ryan Briggs contributed to this article.