Residents in a Manhattan building were concerned for their safety Sunday, a day after a fire claimed the lives of five of their neighbors. NY1's Cindi Avila filed the following report.

On Sunday, neighbors remembered a devastated family through song and through a makeshift memorial of votive candles set up outside Robert Fulton House on 18th Street and Ninth Avenue in Chelsea.

The previous morning, a fire on the sixth floor killed three young children and their parents, Maschay Joa Valdez and Delkis Balbuena.

On Sunday, only their 10-year-old son survived in critical condition in Jacobi Hospital.

Fire officials said the family died of smoke inhalation after the fire started in the kitchen and spread to the living room.

"I opened the door and I saw the smoke, I ran into my kitchen, grabbed my phone and called 9-1-1," said neighbor Nancy Santiago, who lives just across the hall from the site of the fire.

Santiago said she can't believe her neighbors are gone. Her five-year-old daughter used to play with their children.

Now, like many people in the complex, Santiago wants to make sure her own home is secure.

On Sunday, she got help from firefighters, who went from floor to floor checking smoke detectors in the building.

“They put the smoke detector and carbon monoxide detector new, but I'd feel safer if I have one closer to the kitchen,” said Santiago. “Because by the time the smoke gets down the halls with the flames, how are we going to get out the door?"

Santiago feared the family across the hall was trapped by flames that prevented them from getting out.

New York City Housing Authority officials said the smoke detector in the burnt apartment was checked twice this year and worked properly both times.

While the cause of the fire was still under investigation Sunday, fire marshals said the apartment’s hard-wired smoke detector was not working because it had been unplugged from the electrical power source and its battery backup had been removed.

"The best thing we were trying to do was bang on their door, but there was no response,” said Santiago. “So we knew it was either too late, or they couldn’t hear us, or they couldn't get out."

All the neighbors had thoughts and prayers for the only surviving member of the family, who has a very hard road ahead.

"Do you pray ‘Lord, heal him’ or do you pray ‘Lord, take him?’ You know it's going to be devastating. I can't even fathom how he's going to feel," said neighbor Lourdes Rivera.

"I hope some family member does come through even if they live somewhere else,” said Santiago. “Somebody needs to come forth because that little boy is going to need a family member right now."

Janet Torres said her son is classmates with the little surviving boy.

"I told my son maybe they'll have a prayer for the family in school on Tuesday. I hope they have counselors on site because they are little kids and they lost a friend," said Torres.

City Council Speaker Christine Quinn, in whose district the fire occurred, offered condolences and services.

"Sometime this week, my office hopefully with the housing authority and the mayor’s office will have an emergency town hall meeting to talk about fire safety questions, plugging in your fire alarms, batteries and other questions the tenants think need to be raised in light of this tragedy," said Quinn.

Autopsies were conducted Sunday on the fire's five victims, but no final determination was made as to the cause of the fire.