Updated 9:35 PM ET
KANSAS CITY, Mo. A day after a natural gas explosion leveled a popular restaurant, investigators raced to search the rubble and tried to understand how the blast happened despite suspicions that flammable fuel had been leaking, maybe for weeks, somewhere in the busy outdoor shopping area.
Hours before the explosion, witnesses reported a strong smell of gas, and firefighters were summoned to the scene at one point but left without ordering an evacuation.
As the cleanup got under way Wednesday, search-and-rescue crews recovered a body. Mayor Sly James declined to identify the victim, but the mother of a missing restaurant server said her family was awaiting confirmation that the remains were those of her daughter.
More than an hour before the blast, a subcontractor working for a cable company hit a gas line with underground boring equipment. Then something inside the restaurant ignited the fuel, authorities said.
Surveillance video from a nearby travel agency shows a fireball erupting from the restaurant's roof, showering the street with debris and throwing up a cloud of dust and smoke. The blast could be felt for a mile and shattered glass in neighboring buildings.
Fifteen people were injured. Six were still hospitalized Wednesday, James said.
People who live and work in the area reported smelling gas for some time before the accident.
Jeff Rogers was waiting at a bus stop down the street from JJ's when the explosion knocked him and another man to the ground.
He said he had smelled gas although "not strong" at the intersection for the past couple of weeks. Then the odor intensified Tuesday.
William Borregard, who lives with his sister and her fiancDe in the apartment building nearest to JJ's, said he too had noticed a strange smell for weeks that had worsened in recent days. On Tuesday, they called the apartment manager.
"We said it's very pungent, and you should come out here and check it out," he said. "He came over and rapped on the door and said there's nothing to worry about. Stay in your apartment." The blast happened five minutes later.
"We finally called the gas company," Dr. John Verstraete, who works at Plaza Physicians Group next door to JJ's, told CBS. "They came out. They checked inside our building, said that we needed to evacuate. It wasn't two minutes when we were grabbing our stuff and the explosion hit, and it hit you like a shockwave."
But no one alerted the fire department or utility officials to the possibility of a leak until the subcontractor called 911 shortly before 5 p.m. Tuesday to report having ruptured the gas pipe, the mayor said.
Within 20 minutes, a worker for Missouri Gas Energy arrived at the scene, followed later by a backhoe to dig a hole that would allow the gas to vent into the air, MGE Chief Operating Officer Rob Hack said.
Those who remained in the restaurant were urged to leave, Hack said. A gas company employee urged people to evacuate the medical center, too.
The blast happened around 6 p.m. Tuesday, when the dinner crowd would have been filing into JJ's and the many other restaurants in the upscale Country Club Plaza shopping and dining district.
The restaurant was a fixture on the city's culinary scene for more than 27 years. Locals knew it as a prime after-work stop, though it won a broader reputation after receiving consistently high ratings from contributors to Zagat's restaurant guides, both for its food and its long wine list.
The mother of the missing server said fire officials told her that dental records were being used to determine for sure whether the remains found in the rubble are those of 46-year-old Megan Cramer.
Genny Cramer said her daughter wrote poetry and helped establish the first lesbian/gay student group at the University of Missouri-Kansas City. Her identity was first reported by the Star.
"We talked on the phone the day she died," Cramer said. "She said she was doing well and was getting ready for work.
When they learned of the leak, firefighters deferred to the utility since it would have more expertise in assessing the situation, Fire Chief Paul Berardi said.
Richard Kuprewicz, a pipeline safety consultant in Redmond, Wash., said federal law holds the utility responsible for deciding whether to evacuate, but assessing the risk isn't always easy.
Sometimes it's difficult to determine how much gas has been built up. And even highly trained people can underestimate the danger.
"I've seen people who work for gas companies and have gas sniffers, and their bodies are found in buildings," Kuprewicz said. "There is some art and some experience and some training in this stuff."
The subcontractor's company, Heartland Midwest, did not immediately return a call seeking comment.
The Missouri Public Service Commission, which oversees utilities, launched an investigation into the blast, dispatching five employees to the site.
Commission Chairman Kevin Gunn said preliminary information indicates that gas pipelines had been properly marked. It could take up to six months before a final report is issued.