Federal and local officials say a fatal explosion and fire at a Kansas City restaurant last month were sparked by natural gas vapors inside the popular business.

The Kansas City Fire Department and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives said Wednesday the cause of the Feb. 19 blast at JJ's restaurant was the "accidental ignition of natural gas vapors that accumulated" inside the restaurant.

The explosion and fire injured 16 people and killed a 46-year-old woman who worked at the restaurant near the busy outdoor shopping area called the Country Club Plaza.

The Missouri Public Service Commission and the Occupational Safety and Health Administration are conducting a separate investigation into the cause of the natural gas line break near JJ's.