An investigation is underway, but officials in Michigan have confirmed a 5-year-old boy was killed Friday in an explosion at a medical facility.

During a press conference Friday, Lt. Ben Hancock of the Troy, Michigan Police Department said the boy was inside of a hyperbaric chamber when the explosion occurred, killing him. The boy’s mother suffered injuries to her arm as she was standing next to the chamber when it exploded, according to police.

Troy police and firefighters were dispatched to a medical facility located at 165 Kirts Blvd. shortly before 8 a.m. for reports of an explosion. Firefighters were able to contain the blaze to the room where the explosion occurred, officials said.

Lt. Ken Young of the Troy Fire Department said numerous times that it still too early in the investigation to determine what caused the explosion.

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

“Our initial research shows that this is not a common incident and the scene remains under active investigation.”

Young went on to say he expects the investigation will involve multiple jurisdictions and departments throughout the state.

Hancock said it is unknown why the boy was being treated at the facility. Officials did not release the name of the victims.