NEW YORK — The call to Consolidated Edison came at 9:13 a.m. Wednesday: The smell of gas, detectable the night before, had strengthened around two buildings in East Harlem.
Less than 20 minutes later, the buildings were gone, leveled by an explosion whose tremors could be felt more than a mile away.
The blast, which city officials said was touched off by a gas leak, killed at least six people and wounded at least two dozen more, including two critically. Rescue workers continued to search the rubble from the buildings well into the night, hoping to find the nine occupants of the buildings who were still missing.
The explosion blew out windows in surrounding buildings and sent debris crashing onto nearby streets. People were trapped in their cars, in the rubble, and in neighboring apartments. Others rushed toward the towering plume of flames and smoke, making desperate rescue attempts.
There was little warning, certainly not enough to have safely evacuated the area, Mayor Bill de Blasio said at a news conference, near where the buildings once stood.
“This is a tragedy of the worst kind, because there was no indication in time to save people,” the mayor said, warning that the search would take time.
The cause of the gas leak remained unclear Wednesday as a team from the National Transportation Safety Board, which oversees pipeline safety, arrived to help investigate.
Jennifer Salas and her husband, Jordy Salas, lived in one of the buildings. She said Wednesday that her husband and the couple’s dog had been in their apartment at the time of the collapse, and that they were still missing.
Through tears, Salas, who is pregnant, begged firefighters to find her husband.
The couple were among several neighbors who said that they had detected a gaslike odor before, but that it seemed to worsen Tuesday night.
“Last night it smelled like gas, but then the smell vanished, and we all went to sleep,” she said.
Another couple, Shavonne Cano and her fiancé, Corey Louire, said that they had also smelled gas Tuesday night, and that they slept with a window open. When the gas was still noticeable in the morning, they called Con Edison.
Louire said he had been told not to turn on a cellphone or anything else, and to leave the apartment and the building. He was in the lobby when he heard the explosion.
Elizabeth Matthews, a spokeswoman for the utility, confirmed that a customer had called to report a heavy gas odor at 9:13 a.m. Two minutes later, two Con Edison crews were dispatched, and they arrived just after the explosion.
The Fire Department said it had received the first report of a fire at 9:31 a.m. and discovered on arriving two minutes later that the buildings had collapsed. There were a total of 15 apartments in the two buildings. One had a church on the ground floor, the other a piano store.
The buildings were five stories and about 55 feet tall, according to Buildings Department records.
The injured were taken to several area hospitals, where most were treated and released. Officials said 13 people went to Harlem Hospital Center, including a 15-year-old boy in critical condition; 22 people at Mount Sinai Hospital, including a woman in critical condition with head trauma; and 18 at Metropolitan Hospital Center, all with minor injuries.
Later in the day, some corners of the neighborhood had returned to normal. People were walking dogs, music was streaming from passing cars, and young professionals in hospital scrubs clutched cups of coffee from the bodegas near the elevated Park Avenue train tracks. But signs of the trauma remained. Many pedestrians wore surgical masks, a reminder of the panicked scene earlier, when people ran about the area, unsure what was happening as the thick gray smoke blanketed the neighborhood.
Records from the Buildings Department indicate that the rear exterior of the buildings, at 1646 Park Ave., had been found in 2008 to have “several vertical cracks, which is hazardous for the safety of the structure.” The records do not indicate that the hazard was fixed.
Con Ed officials said that there was a report of gas odor at 1644 Park Ave. on May 17, 2013, and that it was determined to be a small leak in customer piping, which was fixed.
The utility routinely inspects pipeline infrastructure across the city — some of which is 127 years old — and officials said that the block where the explosion took place was examined on Feb. 28. No problems were reported.