The body hadn't yet been identified or its gender determined but a female server at JJ's Restaurant had been missing since the explosion Tuesday night, The Kansas City (Mo.) Star reported.
A sous chef at the restaurant was listed in critical condition, said Josh Lehne, a bar manager at JJ's.
Rescue crews and cadaver dogs spent 3 hours Tuesday night searching the scene, said Kansas City Fire Chief Paul Berardi.
He said the explosion and subsequent fire reduced the restaurant to rubble 3 or 4 feet deep that was too heavy to be lifted without machinery.
The fire and explosion injured at least 16 people, officials said.
Witnesses reported a strong natural gas odor in the area several hours before the explosion at 6 p.m. Four employees of JJ's said they began canceling the evening's reservations at 5 p.m. because the smell had worsened and there were relatively few patrons in the restaurant when the blast occurred.
Missouri Gas Energy said a contractor working in the building may have hit a gas line. The company said an investigation was under way.
A self-described regular at the restaurant told KMBC-TV, Kansas City, firefighters and utility representatives were checking for the source of a gas odor before the explosion.
The force of the explosion knocked out windows at least a half-block away and was felt nearly a mile away, the Star reported. Witnesses said flames towered above the building and bricks and broken glass were scattered about.
"It sounded like thunder but it felt like an earthquake," said Tracey Truitt, a lawyer who was working in a nearby building.