Lagos, Nigeria (CNN) -- At least one person died and 40 people were seriously injured in Nigeria on Wednesday when an explosion and fire erupted in a crowded Lagos marketplace, authorities said.
Fireworks in a warehouse sparked a blaze that quickly spread to other buildings in the densely packed city -- the largest in the Africa's most populous nation. The building is thought to be loaded with "knockouts" -- brands of fireworks popular during festive periods.
The fire started in a shop not permitted to store the explosives, said Philemon Leha, deputy inspector general of the Nigerian police. It occurred in a marketplace on the city's Lagos Island -- an enclave filled with highly flammable structures built with wood and iron sheets, police said.
Firefighters, Red Cross volunteers and citizens who volunteered to help put out the blaze suffered injuries, a spokesmen for the Nigeria's National Emergency Management Agency said.
NEMA spokesman Yushau A. Shuaib said it took firefighters more than two hours to contain the blaze, and heavy traffic and crowds posed challenges for first responders. Search and rescue crews found a corpse in the rubble.
Shuaib said it spread quickly because of cramped spaces, poor infrastructure and sweltering heat. He said the blaze sparked a stampede causing injuries.
CNN's Nana Karikari-apau, Neda Farshbaf and Samuel Santamaria contributed to this report