A memorial was held outside the window of a family's apartment in the Bronx where two toddler sisters were killed by exposure to hot steam from a malfunctioning radiator valve.
As night fell over Hunts Point on Thursday, candles lit up a piece of sidewalk outside the city-owned Bronx apartment building where the family was staying while homeless, as neighbors and well-wishers showed up with balloons to remember the girls.
Earlier on Thursday, the Office of Chief Medical Examiner said the cause of the toddlers' deaths was accidental, and was caused by "hyperthermia and thermal injuries due to exposure to hot steam".
Mayor de Blasio has pledged a thorough, multi-agency investigation into the "freak accident". The Fire Department said the radiator valve inside their first floor apartment malfunctioned, sending high pressure steam shooting out to fill the apartment on Hunts Point Avenue shortly after noon Wednesday.
The children, identified as Scylee Vayoh, 1, and Ibanez Ambrose, 2, were severely burned.
At a news briefing Thursday, de Blasio said multiple agencies, including the NYPD and Department of Homeless Services, are investigating what he said appeared to be an "extraordinary and unprecedented accident."
"No one I've talked to so far in any agency has ever seen anything like this," de Blasio said. "We need to understand what happened here. This was a freak accident, a series of painful coincidences that led to the loss of these children."
But neighbors who lived in the same building had growing concerns about their own safety. Inspectors have been to each apartment and checked each radiator, but residents say they had filed complaints about the premise leading up the girls' deaths.
"So it takes a tragedy of 2 little girls to lose their lives for them to come and inspect?," one resident asked. "It doesn't make any sense. Too little, too late."
The mayor said the problem appeared contained to the radiator valve in the children's apartment.
He said an investigation of the apartment building last month yielded no "high priority" violations. And he said there were no specific complaints to the city's knowledge that would have indicated such a tragedy was looming. NYPD officials said Thursday that another routine inspection on Monday didn't reveal anything "untoward."
"We are trying to put the pieces together but so far cannot understand how something like this could have happened," de Blasio said.
Kids' drawings and photos decorated the small apartment where the children lived with their parents, the mayor said, describing the scene as painful to see.
"It was clearly a warm and loving household," de Blasio said.
Neighbors told NBC 4 New York they heard a loud boom at the time of the steam blast and fled the building.
"The babies came out, they were burned all over the body -- burned blue, and there was no fire, so steam coming from somewhere," said Martiza Morales, recalling they "were not moving at all."
The children's parents ran out in tears, neighbors said.
"They were screaming for help. They say the radiator exploded in there," said Annie Martinez.
Martinez said she was supposed to babysit for the children on Thursday, and hasn't been albe to sleep since the explosion. She said she had been complaining about conditions in her apartment for months and nothing was done until after the blast.
"All these tenants have been giving complaints," she said. "All these violations and they didn't do anything about it."
Radio transmissions between the dispatcher and emergency responders revealed a grim scene.
"It looks like it might have been something to do with a heater," the dispatcher could be heard saying. "We don't know if it blew up or what. But a heater injured those two kids, and they're in cardiac arrest right now."
"We got a lot of calls for smoke, so it looks like it might have been steam," the dispatcher added.
The city's social services department said after the blast that the children and their family were among five placed at the apartment building being used as a so-called "cluster site" -- a building with a mix of renters and homeless families. The other families at the apartment were moved to other shelters.
"We are devastated by this tragedy," the department said in a statement. "We are investigating and taking steps to immediately transfer the four other families being sheltered at this location to another shelter.”
Family members tell WCSH-TV the parents moved to New York about a year ago from Maine.
City records show that the apartment where the blast went off had no open violations with the city, but that the building itself had 60 violations. There had been 46 complaints called into 311 this year for the building, including three for radiators."
One of the landlords of the building was on the city advocate's list of the 100 worst landlords. NBC 4 New York has reached out to the landlord's attorney for comment.
In a statement Thursday, New York City Comptroller Scott Stringer said he was outraged by the deaths of the children and called on the city to release a roadmap to tackle the homeless crisis.
"Cluster sites can be extremely dangerous for homeless families. Hotels are extraordinarily expensive and provide limited services. These options make no sense," Stringer said. "That’s why we need a clear, transparent, public plan. While I know that progress will take time, we cannot continue to accept the status quo. The city promised to end its reliance on both of these forms of shelter – and we are no doubt trending in the wrong direction."
Stringer said cluster sites not previously identified for closure have more than 13,000 open violations, including 1,000 that are "high priority."
"What a horrifying loss," he said of the little girls who lost their lives. "My heart goes out to this family in this time of unimaginable pain."
De Blasio said Thursday the city wants to move away from cluster sites, but doesn't want homeless people living on the street. He said his administration would work to develop a timeline and additional strategic planning. In the meantime, he said the city will perform checks at 3,000 cluster sites.
A representative for the non-profit Bedco, which placed the Ambrose family, declined to comment to NBC 4 New York. The city said it was in the process of entering a contract with Bedco to place more homeless families.