At least 12 people were killed when a fire fueled by gusty winds tore through a century-old apartment building in the Bronx on a frigid Thursday night, New York City officials said. It was the deadliest fire in the city in more than a quarter-century.

In addition to the deaths, four people were critically injured and two people sustained non-life-threatening injuries, Mayor Bill de Blasio said at a news conference late Thursday. The youngest among the dead was 1 year old, the oldest over 50.

“Tonight in the Bronx we’ve seen the worst fire tragedy in at least a quarter of a century,’’ the mayor said on Twitter late Thursday. “It is unspeakable, and families have been torn apart.”

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The first emergency call came at 6:51 p.m. for a fire in a five-story apartment building at 2363 Prospect Avenue in the Belmont neighborhood, a spokesman for the New York City Fire Department said. The department responded in three minutes, the mayor said, and firefighters were able to rescue 12 people.

The fire began on the first floor but quickly spread throughout the building, as the wind fed oxygen to the flames. The people who died were on various floors, the fire commissioner, Daniel A. Nigro, said.

The blaze grew to five-alarm status, and more than 160 firefighters responded. By the time Mr. de Blasio spoke, around 10 p.m., the flames had been brought under control.

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The cause of the fire was not yet clear.

It was a bitterly cold night, with temperatures in the teens, and the wind chill made it feel below zero. Water leaking from fire hoses froze in streaks on the concrete, and displaced residents walked around draped in American Red Cross blankets. Three young girls were whisked into a neighboring building after climbing down a fire escape with no shoes or coats.

Officials said they were opening up the nearby Grace H. Dodge vocational high school as a reception center for people who needed housing and other services. People looking for relatives who lived in the building were also told to go to the school, or to call 311.

Luz Hernandez said she first realized something was wrong when the smell of burning rubber filled her apartment on the fourth floor, followed by smoke so thick that the room turned pitch-black. She summoned her husband and two sons, 11 and 16, to the window, and they descended the front fire escape as smoke rose near them.

Later, Ms. Hernandez said in Spanish, she saw the charred bodies of two women who lived together and their two young daughters being carried away on stretchers.

Through the closed windows of a building next door, the smoke seeped into a fifth-floor apartment where Ana Santiago, 25, was cooking dinner.

Ms. Santiago said she called 911 and ran downstairs with her 4-year-old son, knocking on neighbors’ doors as she went. When she reached the street, she saw a man lying on the ground, she said, pointing to a patch of sidewalk where glass shards lay like snow. She could not tell if he was alive or dead.

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“I saw the body, I almost passed out,” she said.

Down the street, under a sign welcoming visitors to Little Italy, Dianna Reyes wailed as she hopped out of a Red Cross vehicle. She said that she had escaped with her daughter and pulled a neighbor’s two children from the fire, but that she had to leave other children behind.

“I had one on my front and one on my back,” Ms. Reyes said, sobbing. “I couldn’t carry the rest of them.”

Thieron Diallo, 59, a Guinean immigrant who lived in a basement apartment, said the tenants of the building — a five-story walk-up near East 187th Street, close to the Bronx Zoo — were a diverse set, including Africans, West Indians and Hispanics.

The building, constructed of plaster and brick, was not fireproof. It was built in 1916 and had more than 20 units, according to property records.

City records appeared to indicate that as of Thursday, the building had six open violations, including one for a defective smoke detector on the first floor. That was the floor where the fire began, Commissioner Nigro said.

The 12 confirmed fatalities made the fire the deadliest since an inferno at the Happy Land social club — less than a mile from Thursday’s blaze — killed 87 people in 1990. It surpassed the toll from a fire a decade ago, in March 2007, when an overheated cord to a space heater caused a fire that tore through a four-story house in the Bronx and killed 10 people, nine of them children.

Elected officials — including Gov. Andrew M. Cuomo; Ruben Diaz Jr., the Bronx borough president; and Rafael Salamanca Jr., the neighborhood’s City Council member — took to Twitter late Thursday to offer their condolences. Mr. Cuomo said he was “closely monitoring” the situation.

Kwabena Mensah, 62, said he had visited four hospitals looking for his son, Emmanuel Mensah, who lives on the third floor of the building. Six others who live in the apartment evacuated safely and were gathered at the elder Mr. Mensah’s home nearby, he said, but his son was nowhere to be found.

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Emmanuel, 28, was stationed in Virginia with the Army and had returned to the Bronx just a week ago for the holidays.

At Prospect Avenue and East 187th Street, Kenneth Kodua stood in a corner store, staring in disbelief at the plastic takeout bag in his hand. He had gone to a nearby restaurant to buy food, he said, telling his roommate he would be back soon. When he returned 20 minutes later, firefighters had swarmed the building and told him he could not enter.

“Just 20 minutes. I told my roommate I’m going to buy food. Within 20 minutes …” he said, trailing off.

Mr. Kodua, 37, said he had called his roommate more than a dozen times, to no avail.

“The phone is ringing, but nothing,” he said, struggling to form words, his eyes glazed. He turned away, toward a deli shelf, tapping his hand on cans of cat food.

“Oh my God,” he repeated to himself. “Oh my God.”

Vivian Wang, Sandra E. Garcia, J. David Goodman, Benjamin Mueller and Matt Stevens contributed reporting.

A version of this article appears in print on December 29, 2017, on Page A1 of the New York edition with the headline: At Least 12 Die in Bronx Inferno, City’s Deadliest Fire in 27 Years. Order Reprints | Today’s Paper | Subscribe