An enormous fire at Central America's largest open-air market Monday killed 15 people, including three minors, and sent up columns of smoke visible six miles away. Witnesses said the blaze was sparked by a lit cigarette.

The fire broke out in an area of illegal fireworks stands set up temporarily near a section of the permanent market where corn and beans are sold year-round, said fire department spokesman Ricardo Lemus, who confirmed the number of deaths. He did not have the ages of the minors, all of whom worked in the permanent market.

The blaze quickly destroyed about 40 of the permanent market's hundreds of shops, which cover a 2- to 3-square-mile area.

Lemus said the cause of the fire was still under investigation. One of the fireworks merchants, Carlos Balam, however, told The Associated Press that it was started by a lit cigarette that he saw one of his fellow vendors throw into the street.

He said a strong wind blew the cigarette back into the stalls, setting off a package of fireworks and sparking a blaze that spread rapidly. "That's what started it all," he said.

Several merchants from the corn and bean markets, who did not identify themselves, told the same story.

Officials said they did not know the exact number of wood, plastic and cardboard stands that sold fireworks along a 100-yard stretch of roadway close to the permanent market. None of them had permission to operate there. Fireworks are popular during the holidays.

Hundreds of firefighters manning 40 trucks arrived at the market, where some merchants stayed inside "instead of taking off running like I did when I heard the explosions," said vendor Roberto Marroquin.

Some of those who stayed behind were asphyxiated by toxic fumes, Lemus said, adding that two firefighters were treated for fume inhalation and burns.

The fire also destroyed more than a half-dozen vehicles.