Related | Girl, 10, found unconscious after roller coaster ride
Coroner's Lt. Fred Corral said Tuesday that Jasmine Martinez had an underlying medical condition and was not injured on the ride at Six Flags Magic Mountain.
Martinez, from Somis, died at a hospital over the weekend.
The girl and a parent were airlifted Friday from the park in Valencia.
The amusement park released a statement that said the girl was found breathing but unconscious after riding the Revolution.
The 113-foot-high looping steel coaster reaches speeds of 55 mph during a two-minute ride.
The Revolution, which dates to 1976, was cleared to reopen shortly after the incident.
Copyright 2015 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.