The death of Miller Gardner, the 14-year-old son of former New York Yankees outfielder Brett Gardner, is being investigated as related to possible carbon monoxide poisoning, Randall Zuniga, director of Costa Rica’s Judicial Investigation Department (OIJ), said in a news conference Monday.

An OIJ spokesperson confirmed to ESPN by text message that investigators believe the death to be accidental rather than the result of foul play.

“Furthermore, this investigation has been closely coordinated with the FBI in the United States,” Zuniga said at the news conference.

Zuniga also said that tests were conducted in “the room the family was staying” on Friday — a week after Miller Gardner was found in his hotel room in a popular resort district — when “high emissions of carbon monoxide contamination were detected.” He said this suggested the death might have been from “inhaling hazardous gases.” He said these were initial findings and that the results of forensic toxicology are still to come.

The room that was tested, according to Zuniga, was adjacent to “a machine room,” which investigators believe is a source of the contamination.

“Levels of up to 600 parts per million were found, when the correct level should be zero in this specific case,” Zuniga said.

The OIJ spokesperson, Juan Pablo Alvarado Garcia, said no additional information about who else was in the room or how the carbon monoxide affected others in adjacent rooms was immediately available. The OIJ told ESPN last week that asphyxiation — once investigated as a potential cause of death — had been ruled out. Miller Gardner’s air passages were not obstructed, but there were traces of vomit, the OIJ said.

The presence of carbon monoxide was the latest turn in the investigation into death of the former outfielder’s youngest son, which the family said posed many questions but provided few answers. Brett Gardner and his wife, Jessica, announced their son’s death on March 23 in a statement released by the Yankees. The statement said Miller had fallen ill, along with several other family members, while on vacation.

Last Monday, the United States Embassy in Costa Rica and the U.S. Department of State confirmed to ESPN the death of a U.S. citizen in Costa Rica on March 21 but offered no additional details on the cause of death.

“Out of respect for the privacy of the family and loved ones during this difficult time, we have no further comment at this time,” a State Department spokesperson told ESPN.

In a phone call on Tuesday with ESPN, Alvarado Garcia said the 14-year-old was with family members who told investigators that they had “gone to eat at a restaurant and that the food had made them sick.” It’s unclear which family members were with him and where the restaurant was located. A study was requested at the Costa Rican Institute for Research and Teaching in Nutrition and Health (INCIENSA). Nearly a week later, OIJ said that the fire department and the Ministry of Health were notified about the contamination.

Miller Gardner played high school football in South Carolina and wore No. 11, which his father donned during 14 MLB seasons, all with the Yankees. Brett Gardner, a popular team leader, was a member of New York’s 2009 championship team and retired in 2021.