The San Pablito fireworks market was especially well stocked for the holidays and bustling with hundreds of shoppers when a powerful chain-reaction explosion ripped through its stalls, killing at least 29 people and leaving dozens more badly burned.

The third such blast to ravage the market on the northern outskirts of Mexico’s capital since 2005 sent up a towering plume of smoke that was lit up by a staccato of bangs and flashes of light. Once the smoke cleared, the open-air bazaar was reduced to a stark expanse of ash, rubble and the charred metal of fireworks stands, casting a pall over the country’s Christmas season.

Mexico State health officials said 72 people were being treated for injuries from Tuesday’s explosion, including for severe burns, in some cases over 90 percent of their bodies. Ten children were among the hospitalized. Authorities have not yet said what may have caused the explosions which took place in Mexico State, which rings the capital.

Survivor Crescencia Francisco Garcia said she was in the middle of the grid of stalls when the thunderous explosions began. She froze, reflexively looked up at the sky and then took off running through the smoke once she realized everyone was doing so. As she ran she saw people with burns and cuts, and lots of blood.

“Everything was catching fire. Everything was exploding,” Francisco said. “The stones were flying, pieces of brick, everything was flying.”