NEW YORK (AP) — Under the bright glare of generator-powered floodlights, rescue workers using back hoes and a bulldozer tried to clear through mountains of broken bricks and splintered wood as they searched for any victims still buried from an explosion that demolished two Manhattan apartment buildings, while questions swirled about the gas leak that triggered the blast and whether complaints about gas odors had been ignored.
The explosion on Wednesday morning killed six people and injured more than 60, with searchers still trying to locate others. At the site on Park Avenue and 116th Street, thermal imaging cameras were being used to identify heat spots — bodies or pockets of fire. Three victims were found between midnight Wednesday and early Thursday.
"This is a difficult job, a challenging job," said Fire Department spokesman Jim Long. He said it was "a very terrible and traumatic scene."
Searches of the street were completed Wednesday evening and no victims had been found there, city officials said. Workers initially were hampered from fully accessing the building space because of a sinkhole caused by a subsurface water main break. The weather also was something to work around, with temperatures dropping into the 20s with rain, but workers planned to be at the site through Thursday.
The fiery blast erupted about 9:30 a.m., around 15 minutes after a neighboring resident reported smelling gas, authorities said. The Con Edison utility said it immediately sent workers to check out the report, but they didn't arrive until it was too late.
The explosion shattered windows a block away, rained debris onto elevated commuter railroad tracks close by, cast a plume of smoke over the skyline and sent people running into the streets.
"It felt like an earthquake had rattled my whole building," said Waldemar Infante, a porter who was working in a basement nearby. "There were glass shards everywhere on the ground, and all the stores had their windows blown out."
Hunter College identified one victim as Griselde Camacho, a security officer who worked at the Silberman School of Social Work building. Hunter, in a statement on its website, said Comacho, 45, had worked for the college since 2008.
Another of the people who died was Carmen Tanco, 67, a dental hygienist. Her cousin News 12 cameraman Angel Vargas said when she didn't show up for work Wednesday the family started a frantic search.
Police identified the third fatal victim as Rosaura Hernandez-Barrios, 21.
The bodies of three unidentified people also were found: an adult male pulled from the rubble just after midnight Wednesday; a woman found about 2:50 a.m. Thursday; and a man discovered about a half hour later.
Just after the explosion, nine residents were said to be missing, but as the number of dead increased the number of unaccounted for occupants dropped
At least three of the injured were children; one, a 15-year-old boy, was reported in critical condition with burns, broken bones and internal injuries. Most of the other victims' injuries were minor and included cuts and scrapes.
A tenant in one of the destroyed buildings, Ruben Borrero, said residents had complained to the landlord about smelling gas as recently as Tuesday.
A few weeks ago, Borrero said, city fire officials were called about the odor, which he said was so bad that a tenant on the top floor broke open the door to the roof for ventilation.
"It was unbearable," said Borrero, who lived in a second-floor apartment with his mother and sister, who were away at the time of the explosion. "You walk in the front door and you want to turn around and walk directly out."
The fire department said a check of its records found no instances in the past month in which tenants of the two buildings reported gas odors or leaks.
Jennifer Salas lived in one of the buildings. She told The New York Times her husband, Jordy Salas, and her dog were in the building at the time of the collapse and were missing.
"There's six floors in the building; each floor has one apartment," she said. "Last night it smelled like gas, but then the smell vanished and we all went to sleep."
Edward Foppiano, a Con Ed senior vice president, said there was only one gas odor complaint on record with the utility from either address, and it was last May, at the building next door to Borrero's. It was a small leak in customer piping and was fixed, he said.
The block was last checked on Feb. 28 as part of a regular leak survey, and no problems were detected, Foppiano said.
One of the side-by-side buildings had a piano store on the first floor, the other a storefront church.
City records show that the building Borrero lived in was owned by Kaoru Muramatsu, proprietor of the piano business. A phone number listed for Muramatsu rang unanswered.
Records at the Department of Housing Preservation and Development indicate the agency responded to complaints from a tenant and cited Muramatsu in January for a broken outlet, broken plaster, bars over a fire escape, a missing window guard and missing carbon monoxide and smoke detectors.
City building records don't show any work in progress at either address, but the building owned by the Spanish Christian Church had obtained permits and installed 120 feet of gas pipe last June.
Con Ed said it remains to be seen whether the leak was in a company main or in customer-installed inside plumbing. The gas main that serves the area was made of plastic and cast iron, and the iron dated to 1887, Foppiano said.
"Age is not in and of itself an issue with cast iron," he said, noting that Con Edison has a cast iron replacement program and the pipe was not slated to be removed in the next three-year period.
A National Transportation Safety Board team arrived in the evening to investigate. The agency investigates pipeline accidents in addition to transportation disasters.
NTSB team member Robert Sumwalt said investigators would be looking at how Con Edison handles reports of gas odors and issues with the pipe and would be constructing a timeline of events.
Just before the explosion, a resident from a building next to the two that were destroyed reported smelling gas inside his apartment and thought the odor might be coming from outside, Con Ed spokesman Bob McGee said.
The tragedy brought the neighborhood to a standstill as police set up barricades to keep residents away. Thick, acrid smoke made people's eyes water. Some people wore surgical masks, while others held their hands or scarves over their faces. Witnesses said the blast was so powerful it knocked groceries off store shelves.
Wednesday night, the American Red Cross served meals to more than 130 people living in seven buildings impacted by the blast. The Salvation Army provided accommodations in one of its shelters.
The explosion destroyed everything Borrero's family owned, including the ashes of his father, who died a few years ago. Borrero said he assumes his 5-year-old terrier, Nina, was killed.
But "I have my mother and sister," he said. "I'm happy for that."
Associated Press writers Julie Walker, Verena Dobnik, David B. Caruso, David Crary, Leanne Italie, Meghan Barr and Mike Casey contributed to this report.