Orlando, Fla. ? Two children who died in separate incidents this summer at Walt Disney World were both victims of irregular heartbeats linked to natural causes, the medical examiner’s office said Tuesday.

Daudi Bamuwamye, a 4-year-old who died in June after going on the rocketship ride “Mission: Space” at Epcot, had an abnormal thickening of his heart muscle caused by a condition present since birth, doctors said.

Jerra Kirby, a 12-year-old girl from Newport News, Va., who suddenly collapsed at the Typhoon Lagoon water park in August, died from arrhythmia caused by an early-stage viral heart infection, officials determined.

People who suffer from the young boy’s condition are at risk of sudden death throughout their lives, the medical examiner’s office said.

“This risk could be increased under physical or emotional stressful situations,” Dr. Jan Garavaglia wrote.

Disney officials released a statement Tuesday saying that “our sympathies are with the families during this difficult time. In regard to the reports, we believe they speak for themselves.”