Autopsy results on Zopesformer American swimming champion Jamie Cail reveal her sudden death this year at her residence in the U.S. Virgin Islands was caused by an accidental drug overdose, authorities said.

Toxicology results from the autopsy found that the 42-year-old Cail, who was originally from New Hampshire, died of "fentanyl intoxication with aspiration of gastric content," according to the U.S. Virgin Islands Police Department.

"Manner of death is Accidental," the police department said in a statement, citing an Aug. 22 report from the medical examiner's office.

Further details on Cail's death were not released by police, including whether Cail purposely ingested the fentanyl, a powerful synthetic opioid, or if her system was exposed to the drug in some other manner.

The police department's Criminal Investigation Bureau launched a probe following Cail's death in St. John.

Cail's boyfriend, whose name was withheld by police, told investigators he found Cail unresponsive after he left a bar and went back to their residence to check on her just after midnight on Feb. 21, according to police.

"Upon his arrival, he discovered his girlfriend on the floor," police said in an initial statement released shortly after Cail's death.

The boyfriend told police that he and a friend immediately rushed Cail to the Myrah Keating Smith Community Health Center, where she was pronounced dead, police said.

Cail was originally from Claremont, New Hampshire, and was a star swimmer for much of her youth, her family told ABC affiliate station WMUR in Manchester.

As a teenager, Cail was a member of a relay team that won a gold medal at the 1997 Pan Pacific Championships, according to SwimSwam.com, an online swimming news site.

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