A Queens facility that serves as a boarding house for Chinese “tourist babies” became a scene of horror early Friday when a worker stabbed three newborns and two adults there before trying to kill herself, police and sources said.

The carnage happened at around 3:45 a.m. in the three-story home in Flushing, where workers provide care to babies born in the US in exchange for thousands of dollars.

One of the employees, identified by law-enforcement sources as Yu Fen Wang, went berserk and attacked a 63-year-old colleague and a 31-year-old man, officials said.

Wang, 52, then stabbed three baby girls — a 3-day-old, a 2-week-old and a 1-month-old, sources said.

The injured man, who was struck in the ankle, is the father of one of those babies, and the injured colleague suffered wounds to her torso, police said.

Wang, who sources said has psychological problems, then fled to the basement of the brick home on 161st Street and slit her left wrist.

Police discovered her unconscious and used a tourniquet to stem her bleeding. They found a butcher knife and meat cleaver at the scene.

All of the injured, including Wang, were in stable condition Friday.

“There was one child more seriously injured than the other two,” NYPD Assistant Chief Juanita Holmes said at a press conference.

“At one point, we thought she might have been likely [to die], but thank God she was upgraded, and she’s currently in critical condition but stable.”

Wang is in custody at a nearby hospital and undergoing a psychiatric evaluation, Queens prosecutors said.

Two 911 calls described a harrowing scene.

“Help, help, help,” one caller begged the dispatcher, according to NBC New York. “Hurry up, because my baby’s already been stabbed twice. Someone came in and stabbed my baby twice.”

A second caller recalled waking to a commotion.

“I’m sleeping . . . and then I heard somebody yelling . . . and then they are killing people,” the person said. “I just saw the blood on the floor . . . and that somebody got hurt.”

A next-door neighbor also heard the mayhem erupt at around 3:30 a.m.

“I just heard the screaming,” the woman said. “She was screaming, ‘Somebody help me, please!’”

The facility is a registered business with the state called Mei Xin Care Inc., but it secretly operated as part of a citizenship scheme known as “birth tourism,” high-ranking police sources said.

Using tourist visas, pregnant Chinese mothers arrive in America to give birth — granting the child US citizenship under the 14th Amendment — and stay in the country for a month or so to hammer out the baby’s birth certificate and passport paperwork.

The parents return to their native country, but once the children become adults, they can petition for their parents to come back over on a green card.

“They deliver the child in the United States. The mother then returns to China and files for citizenship for the baby,” the source said. “Once they have that, the mother applies for citizenship.”

Such birth-tourism schemes are on the rise. In San Gabriel, Calif., for example, 10 mothers and babies were discovered by investigators holed up in a house.

“It’s a mix of things. The citizenship, they want, but the question is, what’s the motivation for having their kid get citizenship?” said Mark Krikorian, the executive director of the Center for Immigration Studies.

“It’s an escape path for some if things go bad. If the kid is an adult, they can sponsor the parent to come in. For others, it’s education.”

Krikorian, whose Washington, DC-based nonprofit advocates for tougher immigration policies, said the practice of birth tourism is perfectly legal.

“As far as whether the actual facility itself is legal or not, that’s more of a municipal or state question,” he said. “If it is illegal, it’s probably not because it’s a citizenship mill or maternity center.”

The Flushing facility is not a licensed child-care program, the Office of Children and Family Services confirmed. Child-care programs regulated by the agency are barred from caring for infants less than 6 weeks old.

“OCFS is saddened by this horrific situation and investigating it as a possible illegal operation,” the agency said.

One Brooklyn mother whose infant daughter was among the injured told NBC New York that she shelled out $4,600 to stay at the facility for a month.

She said her baby will “thankfully” be fine.

In total, nine babies were present in the building at the time of the stabbing — five girls and four boys — and multiple families were scattered inside in living quarters, said Holmes, the NYPD assistant chief. Sources said cribs were found all over the first floor.

Krikorian said families who have the resources buy into birth tourism as a way to set themselves up to settle in the US.

“If you’re giving birth in your twenties or thirties, you’re not going to be retiring anytime soon. When you’re in your forties or fifties, you’ll be able to get a green card,” he said. “It’s not an immediate thing. It’s a longer-term prospect.”

Mei Xin Care has operated as a business for 10 years, according to state Assemblyman Ron Kim, who represents the area.

He said it falsely advertised itself online as a licensed day-care facility, although he didn’t believe workers were doing anything nefarious there.

“This was not a day care. They misled the public that they were fully licensed to be a baby care center in New York,” he said.

“I would almost categorize it as kind of a high-end illegal Airbnb for taking care of babies . . . I think they are able to host the moms, as well. It’s almost like an Airbnb for moms and their babies.”

In Chinese culture, Kim explained, it’s not unheard of for new moms to take a month to recover from birth — a traditional practice called zuo yue zi, or literally “sitting the month” — while receiving help with the baby from a relative.

“But that is a luxury most working families do not have,” Kim said. “So, oftentimes, mothers of Chinese descent rely on outside sources to get that kind of support, creating a business opportunity, in my opinion, for some of these community groups to step in and fill that void.”

The NYPD said it had received no calls to the home, nor had any violations been logged with the city Department of Health.

Just one 311 complaint was filed against the address in 2011 — for children crying.

Additional reporting by Gina Daidone and Kevin Fasick