TROY, Michigan — A pressurized oxygen chamber exploded Friday, killing a 5-year-old patient and injuring his mother at a suburban Detroit medical facility.

The hyperbaric chamber explosion occurred about 8 a.m. at the Oxford Center in Troy, north of Detroit.

The child, from Royal Oak, Michigan, had been inside the machine and was pronounced dead at the scene.

“The mother of the child suffered some injuries to her arms as she was standing right next to the chamber as the explosion occurred,” Troy police Lt. Ben Hancock said. “We don’t know exactly what the child was being treated for at the center today.”

Hyperbaric oxygen therapy increases the delivery of oxygen to a person’s body by providing pure oxygen in an enclosed space with higher than normal air pressure, according to the Mayo Clinic.

The Mayo Clinic says the therapy includes treatment for decompression sickness, serious tissue disease or wounds, trapped air bubbles in blood vessels, carbon monoxide poisoning, and tissue damage from radiation therapy.

Hyperbaric chambers contain 100% oxygen, which is up to five times the amount of oxygen in a normal room, Troy Fire Lt. Keith Young said Friday at a news conference.

“The presence of such a high amount of oxygen in a pressurized environment can make it extremely combustible,” Young said. “We did some initial investigation. This is very uncommon, so we’re not sure what led up to it.”

Staff from the center also were in the room, but no other injuries were reported.

The explosion was contained to the chamber. A fire in the room had to be put out, Young said.

The Oxford Center said in an email that a fire started inside the hyperbaric oxygen chamber.

“The safety and wellbeing of the children we serve is our highest priority,” the center said. “Nothing like this has happened in our more than 15 years of providing this type of therapy. We do not know why or how this happened and will participate in all of the investigations that now need to take place.”

The investigation into the explosion and fire will be turned over to the state, Young said.