Guatemala City ? A fire raged through Guatemala’s largest open-air market Monday, killing 15 people, officials said. Merchants claimed a cigarette touched off the blaze.

The fire broke out in an area of illegal fireworks stands, set up temporarily near a section of the permanent market shops, said fire department spokesman Ricardo Lemus. Fireworks are popular during the holidays.

The blaze quickly destroyed about 40 of the permanent market’s thousands of shops, which are spread across an area more than two square miles in size.

Some merchants stayed inside their stalls to protect their merchandise “instead of taking off running like I did,” said vendor Roberto Marroquin.

Lemus said that some who stayed behind were asphyxiated by toxic fumes. He put the death toll at 15.

Officials said the cause of blaze was still under investigation. But fireworks vendor Carlos Balam told The Associated Press that a still-burning cigarette butt accidentally landed in a fireworks stall.

“That’s what started it all,” he said. Several other merchants, who did not identify themselves, told the AP the same story.

Hundreds of firefighters manning 40 trucks fought the blaze. Lemus said two firefighters were treated for smoke inhalation and burns.

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