At least three people have been killed and dozens more injured after a gas leak caused an explosion that destroyed two buildings in East Harlem on Wednesday morning. Several people were also missing, officials said.

The mayor's office confirmed the third fatality on Thursday evening.

The explosion that reduced the buildings at 1644 and 1646 Park Ave. to rubble trigged a fire that smoldered into the late afternoon and sent debris raining into the streets.

The two people who died were identified as female. The FDNY said two people had serious life-threatening injuries, five had serious non-life-threatening injuries, and 15 people had minor injuries. The victims were being treated at Harlem Hospital, Mount Sinai Hospital, Metropolitan Hospital, and St. Luke's Hospital.

The hospitals, however, reported more victims. Mount Sinai Hospital said 22 people, three of whom were children, had been taken there. The hospital's director of emergency management, Dr. Kevin Chasen, said a woman who had been found in the rubble had critical injuries. Chasen said most of the injuries were minor -- cuts, scrapes, broken bones, and smoke inhalation. Six people had already been released.

Metropolitan Hospital Center said it received 17 patients related to the explosion. Nine adults and one pediatric patient are being held for evaluation and are listed in stable condition.

Harlem Hospital issued a statement saying they had received 13 patients from the explosion. There were ten adult children all in stable condition, and three children, one critical condition and two in stable condition.

A representative from St. Luke's Hospital said they were treating one patient injured in the explosion.

The Red Cross has set up a Reception Center at PS 57 on 115th Street between Third and Lexington avenues.

The National Transportation Safety Board, which investigates pipeline accidents, said it had dispatched a team to the scene of the explosion. The agency said it would be looking at the integrity of the pipeline, as well as how Con Ed responded to complaints about gas leaks.

At a news conference, Mayor Bill de Blasio said the fire was caused by a gas leak. Someone from 1652 Park Ave. called Con Ed and reported they smelled gas at  9:13 a.m., officials said.

He said workers with Con Ed were en route to deal with the problem but "the explosion occurred before the team could arrive."

"This is a tragedy of the worst kind because there was no indication in time to save people," he said, adding that relatives of the victims were still being contacted.

De Blasio said 250 fire personnel responded to the five-alarm fire. One building, 1644 Park Ave., had six units, and the other, 1646 Park Ave., had nine residences. According to records of the Department of Buildings, both buildings were five stories.

FBI spokesman Chris Sinos confirmed in a statement that two agents were injured in the explosion. Sinos said the injuries were not life-threatening.

Speaking outside Harlem Hopsital where many victims had been taken, Diane Cortez said her cousin, Carmen Tanto, lived in one of the buildings.

"I called people; they have no knowledge of her whereabouts," said Cortez, who was hoping the hospital had information about Tanto.

Montserrate Acevedo, 24, said she went to four different hospitals searching for her brother-in-law, who lived on the second floor of 1644 Park Ave.

"It's really, really stressful," Acevedo said. "We haven't heard anything since 9 a.m."

Jeifer Mejia, 21, said his father, Juaquim Mejia, 53, was driving by the building in a green cab when the explosion happened. Juaquim's car was shattered, and they are holding him at Harlem Hospital for observation, but Jeifer said he is "extremely" relieved.

"He was under the train, and he thought the train fell on him," Jeifer said.

Shortly after the fire, the scene was described as chaotic, and people were seen running with from the building covering their faces with their hands to shield from the smoke.

"I heard the explosion, saw the smoke and came to pick [her two grandchildren] up," said witness Margherita Mitin, who was on 116th Street when the explosion occurred. "There are so many things, you can’t risk anything. I was so scared."

Another witness, Lina McBride, a make-up artist who lives on 115th Street, said she was on her way to work when the explosion occurred. "I saw a whole lot of smoke, debris and fire. It was really scary. The ground was shaking and I thought it was an earthquake," McBride said.

Department of Buildings Acting Commissioner Thomas Fariello said there were no complaints against the building. Absolute Piano, the piano store located in a street-level storefront at 1646 Park Ave., updated its website on Wednesday, saying, "due to an explosion, and the collapse of the building, we are currently closed."

Metro-North suspended service due to debris on the tracks, and asked customers to take subways to the Bronx to connect to Metro-North trains. The electrified third rail had been shut off, Metro-North said. The explosion happened nine blocks from the 125th Street station.

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 -- With Newsday and Lauren Holter