Cause of death revealed for star U.S. swimmer Jamie Cail in Virgin ...

Jamie Cail, a retired American athlete, died from fentanyl intoxication with aspiration of gastric content at her residence in the U.S. Virgin Islands, police said Friday.

Cail's boyfriend left a local bar on Feb. 21 to check on the former competitive swimmer and found her on the floor of their residence, officials said. He and a friend got her into a vehicle and took her to the Myrah Keating-Smith Clinic, where she was pronounced dead.

The Medical Examiner's Office determined Cail's manner of death was accidental, police said.

Two milligrams of fentanyl can be lethal depending on a person's body size, tolerance and past usage, according to the Drug Enforcement Administration. The synthetic opioid is 50 times more powerful than heroin.

Before her death, Cail lived on St. John and worked at a local coffee shop, her family told WMUR. She was originally from Claremont, New Hampshire.

Cail started to swim competitively during her childhood, her family told the station. Records show she competed in freestyle and butterfly races, as well as medleys, while swimming for the U.S. at the Pan Pacific Championships and the FINA Swimming World Cup in the late 1990s. 

She won gold at the Pan Pacific Championships and a silver medal at the Swimming World Cup, according to FINA, the swimming federation now known as World Aquatics, which is recognized by the International Olympic Committee for administering international competitions for water sports. 

Cail was also a member of the women's swim team at the University of Maine during the 2000-2001 academic year, according to the university's alumni association.