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 aboutover 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.
"Two Gs is not that big a deal," said Houston-based theme park consultant Randy King, a former safety director at Six Flags, which operates 30 amusement parks.
Disney officials said in a statement that they were "providing support to the family and are doing everything we can to help them during this difficult time." No changes were made to the ride or in who is permitted to ride it.
'We believe the ride is safe in its current configuration," Disney spokeswoman Jacquee Polak said.
More than 8.6 million visitors have gone on "Mission: Space" since 2003, Polak said.
The sheriff's office said the boy, from Sellersville, Pennsylvania, met the minimum 44-inch height requirement for the ride.
The boy's father is Moses Bamuwamye, a finance officer at the United Nations, authorities said.
One other death was reported at Disney World this year. A 77-year-old woman who was in poor health from diabetes and several ministrokes died in February after going on the Pirates of the Caribbean ride. A medical examiner's report said her death "was not unexpected."
Florida's major theme parks not directly regulated by the state, and instead have their own inspectors.