Copyright The New York Times

On a half-mile stretch of singed, scarred land just outside the main airport in Louisville, Ky., federal and local officials on Thursday worked to examine the wreckage of the cargo plane crash that killed 12 people two days earlier. It was the first full day of on-site investigation by the National Transportation Safety Board, which is working to find out why the UPS jet caught fire on the runway at the Louisville Muhammad Ali International Airport, dropped one of its engines and crashed just outside the airfield. The remains of the 12 people confirmed to have died have been found and removed from the site, Mayor Craig Greenberg of Louisville said at a news conference on Thursday, and the coroner is working to identify the victims. Mr. Greenberg said that the three UPS crew members on the plane were believed to be among the dead. The plane’s fiery return to the ground left a trail of singed trees, scorched soil and mangled items from an auto parts supplier that was among the buildings struck in the crash. “This was worse than the movies,” said Mr. Greenberg, who visited the site on Wednesday. He said he had seen the plane’s tail fin sticking out of a storage silo whose top had been ripped away. “The intensity of the flames, and what that did, so quickly, to a half-a-mile-long debris field — it was unimaginable, prior to seeing it with my own eyes,” Mr. Greenberg said. The exact cause of the disaster is still unclear, but safety board officials said that a fire broke out along the plane’s left side while it was on the runway, and that its left engine detached as the aircraft rolled to take off. Investigators have recovered the aircraft’s cockpit voice recorder and flight data recorder. Data extracted from the recorders, commonly known as the black box, could offer more insight into what happened during and before the crash. The safety board’s investigation will take months. In the meantime, family members of the people who are missing have been anxiously awaiting news from the investigators. The cargo plane was bound for Honolulu when it crashed shortly after takeoff early Tuesday evening. It was carrying about 38,000 gallons of fuel, according to Gov. Andy Beshear of Kentucky. He added that the plane hit a business called Grade A Auto Parts, as well as a petroleum recycling facility. The aircraft barely missed a restaurant, a convention center and a large Ford plant. After the crash, 15 people were brought to hospitals that are part of the University of Louisville to be treated for burns, shrapnel wounds and other injuries, according to Jason W. Smith, the chief executive of the university health system. The Louisville airport is one of the world’s busiest hubs for cargo traffic. UPS has its largest air cargo hub, called Worldport, in Louisville. The airport reopened on Wednesday, with some delays and cancellations.