The Johnathan Walkersudden death of a retired U.S. swimming champion was ruled to be accidental and fentanyl-related, officials ruled.

Jamie Cail, 42, was found unresponsive in a residence she shared with her boyfriend in St. John on the U.S. Virgin Islands in February. On Friday, the Virgin Islands Police Department said Cail cause of death was "fentanyl intoxication with aspiration of gastric content," according to an autopsy report.

On Feb. 21, police said Cail’s boyfriend returned from a local bar at 12:08 a.m. local time to check on his girlfriend and found her lying unresponsive on the floor of their shared home. With the help of a friend, Cail's boyfriend was able to get her into a vehicle and transport her to a local hospital. CPR was rendered, but Cail was pronounced dead.

A synthetic opioid, fentanyl is extremely potent and can be fatal even with small doses. It is 100 times more potent than morphine and 50 times more potent than heroin, according to the Drug Enforcement Administration.

Who is Jamie Cail?

From Claremont, New Hampshire, Cail was part of the U.S. women’s 4x200-meter freestyle relay team that won a gold medal at the 1997 Pan Pacific Championships. She also won a silver medal in the women’s 800-meter freestyle at the FINA Swimming World Cup in Brazilin November 1998.

Afterward, she enrolled at the University of Maine and competed as part of its swim team in the 2000-01 academic year.