VICTORIA, Seychelles — Two American sisters found dead in their tropical island villa while vacationing in Seychelles died of excess fluid in their lungs, according to police in the African archipelago nation.

Annie Marie Korkki, 37, and Robin Marie Korkki, 42, were found motionless in the bed of their villa last week by hotel staff at the Maia resort on Mahe, Seychelles’ main island. Police spokesperson Jean Toussaint told local media that the women were seen drinking and were helped to their room by hotel personnel the night before they were found dead.

Autopsies conducted Wednesday determined the Minnesota natives died from acute pulmonary edema, or having fluid in their lungs, according to a police report obtained by Minnesota television station KARE. Cerebral edema, or fluid in the brain, was also cited in Annie Korkki’s death.

The report also said no visible signs of injuries were found.

Police said the autopsies were conducted by a forensic pathologist in the neighboring Indian Ocean island of Mauritius. The investigation is ongoing and toxicology tests are pending, police said.

Many things can cause acute pulmonary edema and cerebral edema, said Dr. Patrick Lank, a Northwestern Medicine assistant professor of emergency medicine in Chicago. Emergency rooms commonly see it in drug overdoses and alcohol poisoning, he said, but it might also come from a viral infection.

“Two people at the same time is odd,” Lank said. “It suggests more of a toxicologic or environmental cause, or a potential infection if they’re traveling together.”

An itinerary found at the Maia hotel indicated the sisters had been touring Africa since Sept. 1, and that they had visited Kenya, Tanzania and Zanzibar before arriving in Seychelles on Sept. 16. Annie Korkki lived in Denver, while Robin Korkki lived in Chicago.

Their brother, Chris Korkki of Lakeville, Minnesota, told The Associated Press on Thursday that his sisters were adventurous women who wanted to experience life to the fullest.

“They were frequent travelers both domestically and internationally,” he said. “They were kind and generous and compassionate, and were wonderful people that had a positive impact on a huge number of people.”

He didn’t immediately return phone and email messages seeking comment Friday.

A spokesman for Seychelles police was unavailable for comment Friday. The Maia hotel released a statement confirming the sisters were found by a hotel employee who tried to wake them. The statement said: “Our thoughts are with the family and friends.”