Cadaver dogs searched through the smoldering rubble of a Kansas City restaurant after a gas explosion sparked a massive blaze Tuesday evening in an upscale shopping district.

More than a dozen people were injured in the blast and resulting fire, which occurred just after 6 p.m. and completely destroyed JJ's restaurant. There were no reports of fatalities by Tuesday night, though authorities cautioned that could change because it was unclear how many people were inside at the time of the blast.

Kansas City Fire Chief Paul Berardi said cadaver dogs were called to the scene because of the size of the conflagration.

"I would always fear there are fatalities in a scene like this," Berardi said.

He said results of the search would take hours and that he expected his crews would be working the scene through the night.

City Manager Troy Schulte said it appeared an accident by a utility contractor had caused the blast, and a statement from utility Missouri Gas Energy late Tuesday reiterated that possibility, but Berardi and others cautioned that the cause was still being investigated.

"This investigation is ongoing," Berardi said. "We do have reports that there was an odor of gas earlier. But, again, this investigation needs to be concluded before we want to speculate on any of that."

Indeed, the smell of gas was very strong in the area hours after the blast. Berardi said the utility stopped the flow of gas about 8 p.m., and utility crews could be seen working in the area after the blast.

Witnesses noted street signs indicated utility work was being done in the area, and a JJ's employee said the restaurant was open but undergoing renovations.

Mayor Sly James was at the scene after the blast, praising the work of first responders.

"The first thing we need to be concerned about is the people that are injured," James said.

Police Sgt. Tony Sanders said the manager of JJ's restaurant was unable to account for three people, but it was unclear whether they were caught in the blaze or had left earlier.

The University of Kansas Hospital was treating six people injured in the blast, said spokesman Bob Hallinan. He said one person was in critical condition, two were in serious condition and two others were expected to be released. He said all of those injuries were traumatic, such as broken bones, rather than burns or smoke inhalation. The final patient there was a burn victim who was transferred from Truman Medical Center, Hallinan said.

Dr. Marc Larsen, medical director of the emergency room at St. Luke's Hospital, which is near the scene of the fire, said they had treated eight people, six of whom were walk-ins with minor injuries. He said two males were in critical condition and would be kept overnight. He said one had extensive burns and another had facial trauma.

Jim Ligon, a JJ's bartender, said he wasn't working Tuesday night but started getting texts and calls from co-workers minutes after the explosion. He said the incident happened during the peak of weekday happy hour, when there is typically anywhere from 15 to 45 people in the bar area as well as three to five tables of diners at the restaurant.

"JJ's has a small staff, a family feel," said Ligon, 45, of Kansas City, Mo. "You see the same 100 people all the time — a bar and restaurant for regulars. We're just really hoping we come out of here OK in terms of injuries."

Ligon said he was on his way Tuesday night to meet up with co-workers at another bar in town to talk about the incident.

The shopping area was established in 1922 by J.C. Nichols. Based on the architecture of Seville, Spain, it includes retail, restaurants, apartments and offices.