NEW YORK (AP) — Rescue workers using dogs and thermal-detection gear searched the rubble Thursday for victims of a gas explosion that killed at least seven people, while investigators tried to pinpoint the leak and determine whether it had anything to do with New York's aging gas and water mains, some dating to the 19th century.
At least five people were unaccounted for after the deafening blast Wednesday morning destroyed two five-story brick apartment buildings in East Harlem. More than 60 people were injured.
Fire and utility officials said that if the buildings were plagued in recent days or weeks by strong gas odors, as some tenants claimed, they have no evidence anyone reported it before Wednesday.
Fire Commissioner Salvatore Cassano said experts would first try to reach the basement — still under rubble — to examine heating units, meters and other equipment that might hold clues to the blast. Then they will work their way toward the street, where Con Edison has a gas main consisting partly of cast iron from 1887.
"We can only get conclusive evidence when the fire is out, when the rescue is completed, and we really get a chance to look at all the facts," Mayor Bill de Blasio said.
Aging infrastructure — crumbling bridges, highways, water mains and gas lines — has become a major concern in recent years, especially in older cities in the Northeast, and has been blamed for explosions, floods and other accidents. But many cities say they just don't have the money to fix the problem.
"We know this is a fundamental challenge for New York City and any older city," de Blasio said. But he added: "This is not the occasion to talk about the dynamics about our national government and the lack of support for infrastructure. ... That's a separate discussion for another day."
As cold, stiff winds blew across the still-smoldering debris, construction equipment with iron jaws picked up the rubble, first depositing it on the pavement, then hoisting it onto trucks that hauled it away. Clouds of thick smoke swirled over Park Avenue.
The mayor told firefighters carrying grappling hooks and other equipment: "I can only imagine, knowing that at any moment you might find a body, how difficult that is."
The seven confirmed dead include Griselde Camacho, 45, a Hunter College security officer, and Carmen Tanco, 67, a dental hygienist who took part in church-sponsored medical missions to South Africa, the Dominican Republic and Nigeria.
Mexican officials said two other victims came from state of Puebla: Rosaura Barrios Vazquez, 43, and Rosaura Hernandez Barrios, 22.
The bodies of three unidentified men also were pulled from the rubble.
At least three of the injured were children. One, a 15-year-old boy, was reported in critical condition Thursday with burns, broken bones and internal injuries. A woman was in critical condition with a head injury.
The blast erupted about 15 minutes after someone from a neighboring building reported smelling gas, authorities said. Con Ed said it immediately sent workers to check out the report, but they got there too late.
Con Ed CEO John McAvoy said the call had been correctly categorized as a low priority. "A single person calling that they smelled gas outside of a building is not something that would warrant a Fire Department response," he said.
After the disaster, a number of neighborhood residents said they smelled gas on Tuesday but did not report it. A tenant in one of the destroyed buildings, Ruben Borrero, said that residents had complained to the landlord about gas odors on Tuesday and that fire officials were called a few weeks ago.
But Cassano and McAvoy said that before Wednesday, the Fire Department and Con Ed had received no complaints in the last 30 days about a gas leak in the area.
De Blasio said that because of the city's old and vulnerable infrastructure, people should heed the post-9/11 slogan "If you see something, say something."
"Every citizen of this city should certainly always tell the city government if they see a problem," he said.
The working-class neighborhood around the site at Park Avenue and 116th Street was once known as Spanish Harlem because of its large population of Puerto Ricans but now has many Asians and other ethnic groups. The neighborhood is gentrifying but still has a high crime rate, fueled by drugs and gangs.
Storefronts range from fast-food shops to "botanicas" selling folk medicine and religious items.
More than 30,000 miles of decades-old, decaying cast-iron pipe are still being used to deliver gas nationwide, according to the U.S. Transportation Department estimates. In 2011, the American Gas Association said replacement or repair could cost $82 billion.
New York City still uses about 3,000 miles of decades-old cast-iron pipe, Boston about 2,000 miles, Philadelphia about 1,500 and Washington 400, the department said. Experts said much of the old pipe dates to before World War II, and some of it may even be more than 100 years old.
Associated Press writers Julie Walker, Jonathan Lemire, Jake Pearson, David B. Caruso, David Crary, Leanne Italie, Karen Matthews, Deepti Hajela, Jim Fitzgerald and Mike Casey contributed to this report.