A 5-year-old boy in Michigan has died after being trapped in a hyperbaric chamber that exploded while he was receiving treatment at a clinic.

Police said they rushed to The Oxford Medical Center in Troy, Michigan, on Friday morning after receiving reports of an explosion and found the child dead inside the chamber. The boy’s mother sustained injuries to her arms as she was near the chamber, but no one else was hurt, CBS News reported.

How Do Hyperbaric Chambers Work?

Hyperbaric chambers serve various medical purposes, including treatments for limbs and tissues. The enclosed space provides pure oxygen to the body under high air pressure, according to the Mayo Clinic.

“A hyperbaric chamber contains 100% oxygen, which is up to five times the amount of oxygen in a normal room,” Troy Fire Department Lt. Keith Young said, per CBS News. “The presence of such a high amount of oxygen in a pressurized environment can make it extremely combustible.”

Investigation Into the Explosion

It is not yet clear what the 5-year-old was being treated for before he died, and the cause of the explosion remains undetermined.

“We do not know why or how this happened and will participate in all of the investigations that now need to take place,” The Oxford Center said in a statement.

The medical center also expressed its condolences, saying it has been “an exceptionally difficult day for all of us.”

“As law enforcement officials have shared, at our location in Troy, Michigan, this morning, a fire started inside of a hyperbaric oxygen chamber. The child being treated in that chamber did not survive, and the child’s mother was injured,” the center stated. “The safety and well-being of the children we serve is our highest priority. Nothing like this has happened in our more than 15 years of providing this type of therapy.”