Carmen Tanco, 67, Griselde Camacho, 44, Rosaura Hernandez-Barrios, 21, killed, Oscar Hernandez, 15, at least two others critically injured, unknown number injured, taken to hospital, after a gas main explodes, collapsing two buildings in East Harlem.

Rescuers using spotlights and cadaver dogs searched for survivors into Thursday morning after a thunderous blast in East Harlem killed six people and leveled two apartment buildings.

At least four women and two men died in the Wednesday morning explosion and collapse of 1644 and 1646 Park Ave.

More than 50 people were injured during the uptown horror that erupted into flames, clouds of dust and smoke, and a desperate search among the rubble of the five-story buildings. Those who weren’t injured were traumatized nonetheless.

“We saw people flying out of the windows,” said Ashley Rivera, 21, as she held back tears. “Those are my neighbors.”

Hospital officials reported at least eight children were among the injured in the 9:31 a.m. gas explosion. Two of the them — one each at Harlem Hospital and Mount Sinai Medical Center — were in critical condition, including 15-year-old Oscar Hernandez, who suffered burns in the explosion.

Nine people who lived in apartments above the Spanish Christian Church are still listed as missing, authorities said.

“It felt like the world shook,” said witness Mustafa Shohataa, 27, who was standing near the buildings on Park Ave. at 116th St.

Authorities identified the women who died in the blast as Carmen Tanco, 67, a dental hygienist, Griselde Camacho, 44, a sergeant with Hunter College’s school safety patrol and Rosaura Hernandez-Barrios, 21. The name and age of the man, who was found early Thursday, were not released.

Camacho, who also was a former police officer in Puerto Rico, was home with her mother when their apartment above the church suddenly collapsed.

“She was one of the few security guards who’d say goodnight,” student Molly Ryan, 28, said of Camacho. “She was always ready with a smile and would say, ‘Get home safe.’ ”

Diana Cortez’s long day of searching for her cousin, Tanco, ended in sorrow when police confirmed she had died.

At one point, Cortez, 56, rushed to Harlem Hospital in hopes of finding Tanco.

“I’m just in total disbelief,” Cortez said Wednesday night, after learning of her cousin’s fate. “I just spoke to her on Saturday.”

Isabel Villaverde, 51, a friend of Tanco’s, described her as “a beautiful person.”

“I was in shock. No one believes this could happen to someone you love,” Villaverde said. “It’s unexpected and a terrible pain. But at least she’s in a better place now.”

Carmen Vargas-Rosa, 65, the administrator of the church, said she was still shaken by the explosion Wednesday night.

“I’ve been involved in the church for 60 years and never seen anything like this,” said Vargas-Rosa. “The only thing that’s keeping me standing right now is the Lord’s help.”

“We ask everyone for their prayers,” she said.

The building came down with such force it shattered windows a block away and registered on the seismic scale at Columbia University, which measures earthquake activity in and around New York City.

Officials said 250 firefighters responded to the five-alarm fire.

Mayor de Blasio blamed a gas leak for the blast, but a source said the explosion was the result of a water main collapsing onto a gas line under the street.

Asked about that account, Con Edison spokesman Michael Clendenin said it wasn’t clear if the water main break came before or after the explosion. Officials did confirm there was a report of a gas leak 18 minutes before the blast.

The city’s gas mains that are run by Con Edison in Manhattan, the Bronx, and Queens are 53 years old on average and 60% of those lines are composed of unprotected steel and cast iron, the most leak-prone material, according to a study released by the Center for an Urban Future, an infrastructure think tank, earlier this week.

The calamity churned up horrible memories for many New Yorkers of the Sept. 11 attacks. One scene seemed to be a sad replay from that terrible day — the sight of terrified people scouring city hospitals for missing loved ones.

“It’s very stressful because we don’t know anything,” said 24-year-old Montserrat Acevedo, who went to four hospitals in search of her brother-in-law, Jordy Salas. “We’re trying to reach him.”

Salas, 23, lived on the second floor of 1644 Park Ave. If he was at home at the time of the blast, he didn’t have a chance to escape, said de Blasio.

“There was no warning in advance,” de Blasio said. “It’s a tragedy of the worst kind because there was no indication.”

Flanked by Police Commissioner Bill Bratton and City Council Speaker Melissa Mark-Viverito, whose district office is less than a block from the blast, de Blasio said the search will continue until everybody is found. De Blasio also vowed to investigate reports from residents that they had been smelling gas for days and made repeated calls to 311.

Among other things, the city will check the work of a contractor who nine months ago installed a gas line from the basement to the fifth floor of one of the wrecked buildings. He was allowed to sign off on his own work under a common practice known as “self-certification,” records show.

City officials said a sinkhole has developed due to a water main break related to the explosion. But Carlos Carabajo, who lived at 1644 Park Ave. for 25 years, said that sinkhole has been there for three or four years.

“It was like the street was buckling,” said Carabajo, 54.

Witnesses told the Daily News they saw flames inside the Absolute Piano store at 1646 Park Ave. just before the explosion.

Fire Commissioner Salvatore Cassano said it will be a while before that can be confirmed.

Jessica Ortega watched firefighters roll in powerful lights as the search went into the night. Salas is her brother-in-law, too, and she feared the worst. “We are very worried,” she said. “We don’t know what happened to him.”

Tulio Gomez said his friend Andrea Pogapoulos also lived in one of the blown-up buildings.

“He’s not answering his phone," Gomez said of Pogapoulos, 41. “We don’t know anything.”

Sarah Borrero, who lived at 1646 Park Ave., said everything she owned is now “rubble.”

“I remember this building that was standing up,” she said. “I can still see it in my mind. And now it’s not standing.” Borrero said she is just thankful her 16-year-old daughter, Kimberly, was at school when the building exploded.

The blast also damaged the Park 95 Deli three doors down, owned by Qusai Hezimeh.

“All the windows were blown out,” said Hezimeh, 32. “Everything was turned upside-down in the store.”

Hundreds of people who live near the site were evacuated, and it was not clear when they would be allowed back into their homes.

Most of the injured were taken to Harlem Hospital, St. Luke’s Hospital, Mount Sinai Medical Center and the Metropolitan Hospital.

Among the injured were two FBI agents who happened to be in the area, FBI spokesman Chris Sinos said. A source said they were driving by when chunks of the buildings fell on their car.

In Washington, Rep. Charles Rangel (D-Harlem), called the calamity “our community’s 9/11.”

“What 9/11 was to the world, this is to me,” he said. “It’s my congressional district.”

The White House said President Obama had been briefed on the situation.

The first sign that something was amiss came at 9:13 a.m., when a woman called Con Ed and reported a gas smell, officials said. Eighteen minutes later, the earth shook.

Justine Rodriguez was sleeping next door when the blast blew out her windows.

“I woke up and there was debris and a white cloud and chunks of the building falling around me,” she said. “I grabbed my cat and ran down the stairs.”

Aisha Watts, who also lives next door to the wrecked buildings, said she was in the bathroom when she heard the blast and suddenly there was sunshine spilling into the apartment. “We have no windows, no walls,” she said.

Rubble from the destroyed buildings sent up a cloud of dust that coated much of the surrounding neighborhood.

Metro-North service to and from Grand Central Terminal was suspended in both directions. Some of the tracks were later reopened and limited service resumed.

The MTA said the 4, 5, and 6 trains were slowed to a crawl due to concerns about “vibrations” from the collapse.

“They’re fine,” said Terri Ciaramello. “It’s the people who left pets behind that are the main concern right now.”