Authorities in the Dominican Republic are awaiting toxicology reports in connection with the mysterious deaths of a Maryland couple found inside their resort hotel room Thursday with prescription pill bottles nearby.

An autopsy found that Nathaniel Edward Holmes, 63, of Temple Hills and Cynthia Ann Day, 49, of Upper Marlboro died after their lungs filled with fluid, leading to respiratory failure, according to a news release from the Dominican Republic’s National Police.

“It’s a bit unusual,” Ramon Brito, a spokesman for the tourism branch of the national police, said about the couple’s deaths. He declined to provide further details while the investigation is ongoing.

The U.S. State Department, which assisted local authorities in contacting the couple’s families and arranging for the transport of their remains, said its officials are in “close contact” with investigators.

In mid-April, the department alerted U.S. travelers to exercise “increased caution in the Dominican Republic due to crime,” following an attack on a Delaware woman inside her Punta Cana resort.

In the couple’s case, the medical examiner’s office is testing blood and tissue samples for any substances they may have consumed, including prescription drugs. Three bottles of pills, including prescription oxycodone in five-milligram doses, were found among the couple’s belongings inside the hotel room.

The police statement described the drugs as “various bottles of high blood pressure medication.” There were no signs of violence, police said.

Holmes and Day arrived May 25 at the all-inclusive Grand Bahia Principe hotel in San Pedro de Macoris on the southern coast of the island nation, about 60 miles southeast of Punta Cana. They were expected to leave five days later.

The couple posted photos of themselves on Facebook enjoying time on the beach, wading in the turquoise blue waters of the Caribbean, riding all-terrain vehicles and cruising on a boat. On May 26, Holmes posted: “Can somebody please loan me $250,000 bcuz I don’t want to come home!!!!!”

Day’s cousin had also been staying at the hotel but left a day before the couple were scheduled to leave, authorities said. When the cousin tried to reach Holmes and Day by phone Thursday, they didn’t respond. The cousin told the hotel, which alerted local authorities, police said.

The Dominican Republic is the preferred destination of more than 2 million North American tourists each year. “We are a safe destination for tourists and work hard to ensure the safety and security of all our visitors,” Brito said.

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