City Manager Troy Schulte said he did not know of anyone being reported missing and had not heard of any fatalities.
Earlier Kansas City police had said the blast was caused by a car crashing into a gas main just after 6 p.m. Fire officials said later they were not aware of a crash being involved in the blast. Other witnesses noted street signs in the area indicated utility work was being done in the area, and a worker at a restaurant destroyed in the fire said the facility was being renovated at the time.
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 first thing we need to be concerned about is the people that are injured," said Mayor Sly James, who also praised the work of first responders. James said officials were in contact with Missouri Gas Energy.
The University of Kansas Hospital was treating five 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 the injuries were traumatic, such as broken bones, rather than burns or smoke inhalation.
Kerry O'Connor, a spokeswoman for St. Luke's Hospital, which is near the scene of the fire, said several patients were on the way to the hospital. She said they haven't been assessed yet but "they appear to be critical at this time."
Fire officials didn't immediately return a phone call seeking comment Tuesday evening.
The smell of gas remained very strong near the area long after the suspected explosion.
There were signs that utility work was being done in area. A phone message left Tuesday seeking comment from Missouri Gas Energy was not immediately returned.
Jim Ligon, a bartender who has worked at JJ's restaurant for five years, wasn't working Tuesday night but said he 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.
Video showed dozens of firefighters and other emergency responders battling a massive blaze that appeared to have engulfed an entire block, with flames burning through the roofs. Black smoke swirled in the air and debris littered surrounding streets.
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.
Associated Press reporters Heather Hollingsworth reported from Kansas City, and Jeff McMurray reported from Chicago.