CHICAGO (CBS) — A Chicago woman and her sister are the subjects of a mysterious death investigation at a luxurious resort on an island paradise off the East African coast.

Robin Korkki, 42, and her sister, Annie Korkki, 37, of Denver, were found dead in their room on Sept. 22 at an upscale resort on the Seychelles, a tropical island chain in the Indian Ocean, about 900 miles east of Kenya.

A friend told CBS Chicago the sisters had been traveling in Africa for a month before they were found dead. They had been scheduled to return home on Sept. 24.

According to The Seychelles Nation, the national newspaper, hotel staff found the women in their beds. There were no signs of a physical altercation, but police removed undisclosed prescription medication from their room as part of the investigation.

Robin and Annie Korkki on vacation in the Seychelles. (Source: Facebook)

Robin and Annie Korkki on vacation in the Seychelles. (Source: Facebook)

Police told the paper the sisters were drinking the day before, and needed help getting back to their villa at the resort.

A lifelong friend of the sisters says she suspects foul play in the sisters’ death.

“I think that something nefarious happened,” says Meri Jane Smith, who tells WBBM Newsradio she grew up with Robin and Annie in Minnesota

“There was a Facebook post — it’s on Annie’s Facebook page — that said they were hosting a full moon,” Smith says. “They were going to have a full moon party in their villa and have massages, and that they’d invited the hotel staff to join them in their villa.

“And two days later they were reported dead.”

Smith says she’s seen people speculate about suicide and drug use. But she says “that was not their M.O.” She says Annie, who lived in Denver, had just fallen in love.

A friend of Annie Korkki told CBS Denver the vacation meant the world to her.

“She talked about it as a trip of a lifetime, and I think she and Robin really felt like it was a wonderful way to celebrate their relationship and their love of travel and adventure,” said Caitlyn Cattelino, who coached Annie’s synchronized skating team in Denver.

The sisters posted several photos of their vacation on Facebook.

Their brother said the women were generous, kind, and lived life to the fullest. He said the family has traveled to the Seychelles to recover the sisters’ bodies and learn more about the investigation.

The U.S. Embassy is investigating.

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