LAS VEGAS – A 12-year-old California girl found unconscious after a ride on a Las Vegas Strip roller coaster has died.

The Clark County coroner's office says Catlynne Shaw of Union City, Calif., died Tuesday.

A coroner's spokeswoman says it could be several weeks before a cause of death is determined.

Authorities had said they thought Shaw suffered a heart attack during the July 16 ride on the Canyon Blaster at the Circus Circus Adventuredome.

An off-duty Clark County firefighter was credited with helping resuscitate Shaw before paramedics arrived and she was taken to University Medical Center.

A spokeswoman for MGM Mirage Inc., which owns Circus Circus, says the roller coaster opened in 1993. It can reach a maximum speed of 55 miles per hour and includes a 45 degree drop.