When the ride ended, the boy was limp and unresponsive. She carried him off the ride, and paramedics and a theme park worker tried to revive him, but he died at a hospital.
An autopsy Tuesday showed no trauma so further tests will be conducted and a cause of death may not be known for several weeks, said Sheri Blanton, a spokeswoman for the Medical Examiner's Office in Orlando.
The $100 million Epcot ride, one of Disney World's most popular, was closed after the death but reopened Tuesday after company engineers concluded that it was operating normally.
"Mission: Space" spins riders in a giant centrifuge that subjects them to twice the normal force of gravity, and it is so intense that some riders have been taken to the hospital with chest pain.
The ride recreates a rocket launch and a trip to Mars. A clock counts down before a simulated blastoff that includes smoke and flame and the sound of roaring rocket engines. The G-forces twist and distort riders' faces.
An audio recording and a video warn of the risks. Signs advise pregnant women not to go on the ride. Motion sickness bags are offered to riders. One warning sign posted last year read: "For safety you should be in good health, and free from high blood pressure, heart, back or neck problems, motion sickness or other conditions that can be aggravated by this adventure."
On average there have been about over the past two decades, CBS News Correspondent Byron Pitts reports.
After the accident, Rep. Ed Markey (D-Mass) renewed his push for federal oversite of amusement ride safety.
"The federal government should have some ability to investigate those rides and ensure that they are safe for children," Markey said.
For now, amusement park rides are regulated by state law, and industry insiders say it should stay that way, Pitts reports.
Many consumer advocates agree that the biggest and scariest amusement park rides are relatively safe. Surprisingly, most injuries occur on rides designed for the smallest children.