A 28-year-old Fontana woman apparently suffered a heart attack and died Saturday morning after riding Goliath, Six Flags Magic Mountain's newest roller coaster, a park spokesman said.
Shortly after the park opened at 10 a.m., the woman, whose name was withheld by authorities, and her cousin were strapped into an orange two-seat compartment and zoomed off on the popular steel coaster that reaches speeds up to 85 mph.
Less than three minutes later, when the ride coasted to a stop, the victim was unconscious, authorities said.
Los Angeles County paramedics treated her for a heart attack, authorities said, and she was rushed to Henry Mayo Newhall Memorial Hospital, where she was pronounced dead.
"It appears to be related to some kind of medical problem," said Los Angeles Sheriff's Deputy Richard Westin. "It is not related to a ride. It wasn't that she was thrown from a roller coaster or struck by something."
The victim's mother, Juanita Santos, said her daughter had no history of health problems.
A spokesman for the Valencia amusement park said it was the first such death at the park.
"Nothing like this has ever happened here," spokesman Andy Gallardo said. "It's a very unfortunate occurrence, and our thoughts go out to the family."
The ride was shut down, inspected and reopened several hours later, he said. Sheriff's homicide detectives were at Magic Mountain but only because there had been a death at the amusement park, Westin said.
"There was no sign at all of foul play," Westin said.
Goliath open Feb 11, 2000, and is one of the most popular rides in the park.