Anna Kepner's Death on Carnival Cruise Ship Ruled a Homicide, Report Says: 'Mechanically Asphyxiated'

Anna Kepner's manner of death aboard a Carnival cruise ship has been ruled a homicide, according to reporting by ABC News, which obtained a death certificate from the Florida teen's family.

According to the document, Kepner's death was caused by “mechanical asphyxia,” adding that she was "mechanically asphyxiated by other person(s)." The date of her fatal injury is listed as Nov. 6.

Kepner's body was found under a bed by a housekeeper on the Carnival Horizon. She'd been on the cruise her father, stepmother, three stepsiblings and grandparents.

The night before she went missing, Kepner told her family she wasn't feeling well before going to her room.

The FBI has been conducting the investigation into her death, which occurred on international waters.

A court filing submitted by Kepner's stepmother, Shauntel Hudson, connected to a custody dispute with her ex-husband, previously acknowledged that one of the 18-year-old's stepsiblings could potentially be charged in connection with her death.

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Hudson's filing was in response to an emergency motion filed by her ex, Thomas Hudson, stating that their "sixteen year old child is now a suspect in the death of the step child during the cruise."

The FBI is investigating the case, the agency previously told PEOPLE. Officials have not named a suspect or a person of interest.

Kepner's grandparents said in a recent interview with ABC that the teen and her stepbrother were very close, likening them to "two peas in a pod."

The stepbrother appeared very upset after Kepner's body was found, her grandmother Barbara Kepner told ABC News in an exclusive interview.