Five Americans vacationing in the Dominican Republic and Fiji have died in separate incidents – leaving investigators to determine their cause of death.

The Centers for Disease Control and Prevention is actively investigating the deaths of two American tourists in Fiji. Authorities confirm tissue samples are on their way to CDC headquarters for testing.

David and Michelle Paul of Texas arrived in Fiji on May 22. They died days apart after becoming sick at the resort.

Three Americans died within days at Bahia Principe resorts in the Dominican Republic. Miranda Schaup-Werner checked into the resort with her husband on May 25. She later collapsed, and died shortly after. Five days later, hotel employees found Maryland couple Edward Holmes and Cynthia Day also dead.

All three died from respiratory failure and pulmonary edema. Toxicology reports are pending, but a theory is that the deaths are linked to alcohol in mini bars in their rooms.

Dominican Republic president of hotels and tourism Paola Rainieri says in a statement, “Ambassador Burstein just said yesterday that the Dominican Republic is a safe place to come to visit and that we have all been working together and with the embassy all throughout this process to make sure that everything is clarified, and that an answer to these events does come out."

Meanwhile the deaths have left some Americans planning vacations uneasy about traveling. Peter Scocca, president of New Jersey-based Vista Travel, says that tourists just need to be a little cautious.

"I would probably recommend in light of what's happening here that if clients of mine were to go to an all-inclusive resort I’d probably recommend that they take a drink back from the bar with them in hand versus going to the minibar,” he says. “You have no idea how often that liquor in the mini bar is rotated it could've been sitting there for several years."

Travelers can check to see if the U.S. government has issued a warning for a location before they book their trip. The Dominican Republic currently has a rating of 2 out of 4, which means Americans use caution before traveling there.