A Royal Caribbean cruise ship returned to Baltimore on Monday after a passenger informed staff that his 62-year-old wife was dead in their stateroom Sunday.
The FBI is now investigating the matter.
The ship issued a statement saying that they got in touch with the FBI immediately after learning of the death and also called local police.
The identities of the man and woman have not been released.
They were on a cruise called the Enchantment of the Seas, which includes seven nights, stopping at Port Canaveral, Florida, Nassau and CocoCay Bahamas.
When the ship returned to Maryland, the FBI started its investigation.
They said that there are "suspicious undertones" surrounding the death.
The deceased is from Midlothian, Va., a town outside of Richmond.
"It's a death of undetermined causes," FBI spokesman and Special Agent Rich Wolf said.
Reports indicate that the man found his wife unresponsive on Sunday when the boat was off the coast of North Carolina.
"The ship was working with us the whole way," Wolf said. "We met the ship Monday at 7 a.m. in Baltimore.
Royal Caribbean sent their condolences to the woman's family.
"We extend our most sincere and heartfelt condolences to the family and friends of the 64-year-old female guest from the United States who died while onboard Enchantment of the Seas," a statement said.
When the ship arrived, FBI completed interviews with some of the passengers. The ship left again on Monday evening.