Miller Gardner, the teenage son of former New York Yankees outfielder Brett Gardner, died of carbon monoxide poisoning, authorities in Costa Rica said Wednesday night.

Miller Gardner, 14, died March 21 while the family was vacationing in Costa Rica and the cause of his sudden death was unknown before local officials conducted testing and found carboxyhemoglobin to be the cause. Brett Gardner said in a statement on March 23 that his son died in his sleep, but the family was in shock with no answers on his cause of death.

On Wednesday night, local authorities in Costa Rice said Miller Gardner’s organs presented a “layer” that would indicate carbon monoxide binding to hemoglobin in the bloodstream at a concentration level well over the typical fatal maximum of 50 percent.

Local officials previously ruled out asphyxiation as a cause of death and autopsy results revealed a carbon monoxide level of 64 percent, according to Randall Zuniga, the director of Costa Rica’s Judicial Investigation Agency. He also noted the family was housed near an equipment and machine room at the beachfront hotel where the Gardners slept.

“It’s important to note that adjacent to this room is a dedicated machine room, where it’s believed there may be some type of contamination toward these rooms,” Zuniga said Wednesday.

Brett Gardner played 14 seasons with the Yankees (2008-21) with a career .256 batting average, 139 homers, 274 stolen bases, 578 RBIs and 73 triples.