You can now read 10 articles each month for free on BostonGlobe.com.

The Boston Globe

Nation

Spectators detail fireworks horror in Southern Calif.

California officials investigated the site where a fireworks explosion injured more than three dozen on Thursday.

Nick Ut/associated press

California officials investigated the site where a fireworks explosion injured more than three dozen on Thursday.

SIMI VALLEY, Calif. — When a July Fourth fireworks display exploded and sent red and white bursts into spectators at a Southern California park, Paulina Mulkern saw shrapnel headed straight for her 4-year-old cousin.

Mulkern pushed the girl under a lawn chair and then shielded her 7-year-old cousin with her body as scorching debris flew overhead.

Continue reading below

‘‘You feel the big old heat come right over your back,’’ she said Friday, still shaking as she recounted the explosion the night before that left her hospitalized with bruises and red marks on her back.

At least 36 people were injured as many in the crowd of thousands fled for safety. The victims, from 17 months to 78 years old, had burns and shrapnel wounds, and some were trampled, authorities and hospital officials said.

The injured included 12 children.

Police in Simi Valley, northwest of Los Angeles, said it appeared a firework exploded prematurely in its mortar, knocking over others and aiming them across the field.

Fire investigators, however, said later they had not yet determined a cause.

You have reached the limit of 10 free articles a month

Stay informed with unlimited access to Boston’s trusted news source.

  • High-quality journalism from the region’s largest newsroom
  • Convenient access across all of your devices
  • Today’s Headlines daily newsletter
  • Subscriber-only access to exclusive offers, events, contests, eBooks, and more
  • Less than $1 a week