An 11-year-old boy fell 30 feet from an escalator at the Roosevelt Field mall Sunday, sustaining a serious head injury and landing on his mother, who also was hurt, Nassau County police said Monday.

The boy was inside the Neiman Marcus store at the East Garden City mall at about 3 p.m. and was hanging onto the outside portion of the escalator’s railing as it was moving upward, police said.

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When he reached the top, he fell approximately 30 feet, striking his mother, 33, and injuring her foot.

A police spokesman Monday could not immediately say how the boy got on the outside portion of the railing.

Both were taken by Nassau County ambulance to a hospital for treatment, police said.

Ginger Reeder, a spokeswoman for Neiman Marcus, in a statement called the incident “a tragic accident,” and said the company was cooperating with police during their investigation.

“We are currently reviewing the incident to see what, if any, additional safety measures need to be put into place,” Reeder said.