The inseparable sisters were on a month-long vacation in Africa.
An autopsy has showed two Minnesota sisters both died of acute pulmonary edema, a buildup of fluid in the lungs while on vacation in a hillside villa in a luxury resort in Seychelles, off the coast of Africa.
Read: American Sisters Found Dead in Their Villa at Luxury Resort
One sister additionally had cerebral edema, which is fluid in the brain.
Ann Marie Korkki, 37, and her 42-year-old sister, Robin Marie, have become the center of a baffling mystery. They were found dead in the same bed by hotel staff who said the sisters were drinking heavily the previous day.
No visible signs of injuries were found on the bodies.
The pair had reportedly been helped to their room by staff after spending the day drinking at the resort, which they originally planned to leave on September 22, but extended their stay for two more days.
Pulmonary edema is often linked to poisons and to drug overdoses but how could both sisters die at the same time from the same cause. Could there be foul play?
Forensic pathologist Dr. Bill Mannion told Inside Edition: “To have 2 people die simultaneously, it is not going to be natural causes. They both didn’t have a heart attack at the same time or a stroke at the same time."
He added: “There is no sign of trauma, there is no sign of suffocation, there is no sign of sexual assault. Nothing was stolen, according to the police investigators.”
There is speculation that they died from a lethal combination of alcohol and drugs.
The fun-loving sisters were on a month-long vacation at Maia Luxury Resort and Spa that included an African safari and a stay at the $2,000 a night resort in Seychelles.
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Now their brother, Chris, has traveled to the Seychelles looking for answers, and to bring his sisters home to Minneapolis.
He said they "definitely wanted to experience life to the fullest” and "two things keep going through my mind: This isn't happening, and we just want answers."
Ann worked as a senior administrative assistant for JPMorgan Chase in Denver, while Robin was based in Chicago where she worked as Head of FX and Metals at Allston Trading, according to their professional websites.
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