Gue Verlien, a municipal coordinator for Haiti's Civil Protection Department, said those hurt were taken to two government-run hospitals and a medical center run by the international humanitarian group Doctors Without Borders.
Some of the burns were severe, and some people were being treated for asphyxiation.
A preliminary investigation showed the fire somehow ignited through a combustible combination of Clorox and fertilizer, Verlien said.
Nadia Lochard, another official from the Civil Protection Department, said police were still opening an investigation to learn the exact cause of the fire.
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A market next door that sells used clothes also caught fire, and several trucks and motorcycles parked outside were burned.
Witness Abel Wilson said he heard a loud bang just before the fire broke out.
He also said he saw medical workers treat at least two people for severe burn wounds before an ambulance took them to a hospital for further treatment.