A toxicology report after his death found high levels of carboxyhemoglobin, an indicator of carbon monoxide in the blood, according to a statement from Randall Zúñiga, the director of the Costa Rica Judicial Investigation Agency. Miller Gardner’s test showed a saturation of 64 percent, he said, adding that anything over 50 percent was lethal.

Officials in Costa Rica confirmed Wednesday that the official cause of death for 14-year-old Miller Gardner was carbon monoxide poisoning.

Brett Gardner's son Miller's cause of death has been confirmed by local authorities nearly two weeks after his death. Miller was in Costa Rica with family when he died on the morning of Friday, March 21.