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.

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.

A blood test for carbon monoxide showed a saturation level of 64% in Gardner’s body, Costa Rican officials said. Concentrations above 50% are considered lethal.