Mystery as woman dies moments after family members heard her screaming for ‘unknown reason’ while snorkeling

MYSTERY surrounds the death of a Seattle woman who passed away while snorkeling in a national park on Thursday, officials said.

Moments before she died, family members heard Carol Murrell Maillet screaming for "unknown reasons" as she snorkeled along a beach in Dry Tortugas National Park near Key West in Florida, the Monroe County Sheriff's Office said.

After the 74-year-old woman was brought to the shore, bystanders attempted to perform CPR on the beach.

Maillet was eventually airlifted to a medical center on a nearby island in the Florida Keys on the Gulf of Mexico, according to officials.

She was pronounced dead around 2.47pm on Thursday, police said.

Officials said Maillet had not been on a guided snorkeling trip when the incident occurred as she swam along the Fort Jefferson wall by the beach.

“There was a family member in the water and other witnesses around,” MCSO spokesperson Adam Linhardt told the .

A cause of death has not yet been released, but officials from the sheriff's office said autopsy results are pending.

Authorities do not believe foul play was a factor in the death.

This is the third time this week that a visitor has died while exploring the Florida Keys waters.

In separate locations off Islamorada, two men aged 68 and 72 died in diving incidents.

The investigation into Maillet's death is still ongoing, police say.