Of the 14 people injured, five were critically hurt and two have life-threatening injuries. The Associated Press is reporting that three people are unaccounted for, as well.
Patients are being taken to KU Medical Center, Truman Medical Center, Research Medical Center and St. Luke's on the Plaza.
Fire officials from Johnson County and Kansas City, Kan., sent crews to provide the Kansas City, Mo., Fire Department with assistance.
A Missouri Gas Energy spokesperson confirmed the company services JJ's, and that crews are on the scene trying to turn off the gas. He wasn't sure if any MGE employees were injured in the blast.
Jennifer Carter was having coffee with JJ's manager Matt Nichols shortly before the explosion.
She said nine to 10 people were in the restaurant when she arrived at 5:15 p.m. She said it smelled like gas inside, and JJ's employees had already turned off appliances when gas workers came in with a detector and told everyone to leave.
Carter said she had walked three blocks to away to the Capital Grille when she heard the explosion. She said she called Nichols and he said he was fine, "but there's people covered in blood."
A woman who lives on the same block of JJ's said she smelled smoke about 15 minutes before the fire broke out.
One viewer tweeted us that he felt his house shake from the explosion. He lives at 57th & Locust.
Another viewer tweeted that he felt the explosion at 44th and Pennsylvania: "It was like someone was trying to break in my sliding door!"
JJs Restaurant, owned by Jimmy Frantzè, is one of the longest independently operated restaurants in Kansas City. It opened in February of 1985. Zagat has rated it "one of the top restaurants" in the Midwest, and Wine Spectator named it "one of the best wine lists in the world."
Frantzè told us he was in Oklahoma when the blast occurred, and he's now on his way back to Kansas City.
Police have set up a command post at 47th and Roanake. ( READ MORE )