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.