The boy was receiving medical treatment at a Michigan medical facility when the chamber exploded on Friday, the authorities said. His mother was also injured.

A hyperbaric chamber exploded at the Oxford Center in Troy, Michigan, killing a 5-year-old boy being treated and injuring his mother. What to know about the equipment.

Meanwhile, investigators are trying to determine what caused the explosion. While uncommon, the chamber contains 100 percent oxygen inside, which makes it highly combustible.