-- The discovery of two American sisters dead in their hotel room turned the vacation of a lifetime in Africa into a heartbreaking tragedy.
An autopsy determined the cause of death for both sisters as "acute pulmonary edema," a build up of fluid in the lungs. The autopsy determined that Annie also suffered a "cerebral edema," a swelling in the brain.
The sisters were described as "loving sisters and best friends." They often shared details of their travels to exotic locations on social media, and Annie had posted photos on Facebook just days before the hotel announced the tragic discovery.
The sisters were discovered "when an employee of the hotel tried to wake them" in their villa, according to a statement from the hotel.
The day before their bodies were discovered, the pair had been seen drinking at the resort until about 6:45 p.m. and were later helped to their rooms by staff at 8:15 p.m., according to local news reports.
When the sisters were discovered the next morning, on Sept. 22, "no visible signs of injuries were found on the bodies," according to the police report.
Medications found in the sisters' room have reportedly been confiscated as part of the investigation, which will also include a toxicology analysis.
ABC News has confirmed the sisters' mother and brother have traveled to the Seychelles to bring home the bodies of Robin and Annie.