The US Federal Bureau of Investigation and Massachusetts police are investigating the death of two tourists on the Norweigan Dawn.The cruise ship arrived in Boston, Massachusetts yesterday morning after a trip from Bermuda. Foul play is not suspected in the deaths.A 67-year-old woman ‘s death was quickly ruled to be natural and her body was quickly removed from the ship.A 23-year-old man’s stateroom was processed for evidence as his death had been treated as potentially suspicious because of his age.Their deaths followed the death of a female guest who succumbed to a chronic illness shortly after the ship, with 4,000 people aboard, left for Bermuda on October 21.