Costa Rican Officials Raid Hotel Where Ex-Yankee Brett Gardner Son Died

Officials have conducted a raid at the Costa Rican hotel where former New York Yankees outfielder Brett Gardner's son, Miller, died ... as investigators look into whether the matter is a manslaughter case.

According to ESPN -- which spoke to prosecutor Kenneth Alvarez -- a three-hour search of the Arenas Del Mar Beachfront & Rainforest Resort in Manuel Antonio took place on Thursday to collect more evidence -- both physical and digital.

14-year-old Miller died on March 21 after falling ill while vacationing with his family ... and an autopsy determined carbon monoxide was the cause.

Alvarez said at the time, toxic substance measurement tests were taken ... and Thursday's raid was a follow-up on those results.

The search targeted the management, maintenance and accounting offices at the resort ... and officials say they have also spoken with employees, who have been cooperative.

Initially, it was reported he died from asphyxiation and food poisoning -- before officials later determined a machine room next to the family room likely led to his passing.