Sunrise on the beach at the Gran Bahia Principe resort in the Dominican Republic. File picture: Joe deSousa/Flickr
An investigation is underway in the Dominican Republic, after three US citizens were found dead in a resort in the Dominican Republican city of La Romana at the end of May. All three had checked into the Bahia Principe Hotel resort on May 25, according to CNN.

It remains unclear whether the three deaths, of a Pennsylvania woman and a Maryland couple, are connected, but US officials said they are actively monitoring the investigations.

Miranda Schaup-Werner, 41, who was celebrating her 10th wedding anniversary, died the day she checked into the hotel. Schaup-Werner family spokesman Jay McDonald said she had a drink at the hotel bar shortly before becoming ill. Dominican officials told the family that the cause of death was "pulmonary oedema and respiratory failure" - the same cause attributed to the Maryland couple.

Dominican officials declined to confirm those findings to The Washington Post and said toxicology tests were still pending.

McDonald said initially that they understood that local authorities refused to run toxicology tests, but were later moved to run them.

The family declined to make any further comment.

The Maryland couple - Nathaniel Edward Holmes, 63, of Temple Hills, and Cynthia Ann Day, 49, of Upper Marlboro - were found dead in their hotel room May 30, with prescription bottles of oxycodone in 5-milligram doses nearby. The pills are usually used for high blood pressure.

An autopsy showed that both died when their lungs filled with fluid, leading to respiratory failure, according to a news release from the Dominican Republic's National Police. The pill bottles remain a subject of inquiry.

There were no signs of violence, according to Dominican officials.

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!!!!!"

More than 2 million North American tourists flock to the Dominican Republic every year. But after an attack on a Delaware woman inside her Punta Cana resort in the country in mid-April, the State Department alerted travellers to exercise "increased caution in the Dominican Republic due to crime."

The Washington Post