Local police told Italian media the Asian woman found in Rimini most likely died of starvation, showing signs of extended physical suffering.
It was suspected that the body was linked to Chinese-born Xing Lei Li, who disappeared when she boarded a cruise ship with her husband Daniel Belling and two children on February 10.
It has now been ruled out the woman found has any connection to the ongoing investigation, following an autopsy.
Italy's Ansa news agency stated that authorities are now "certain" the body is not that of Ms Li.
Police found no evidence of a violent death and believe the woman, who is yet to be identified, may have been close to death when she was put into the suitcase.
"She looked as if she'd come out of a concentration camp," the news agency quoted.
The body is understood to be six or seven inches taller than that of Ms Li and would have not been in water longer than 10 days.
Ms Li went missing more than one month ago.
A passer-by discovered the remains of the woman, locked in a blue suitcase on Saturday and raised the alarm.
The suitcase in which the woman was found also does not match that of Ms Li, which has been missing since her disappearance.
Her suitcase was orange and black, while this one is understood to be blue.
Mr Belling's lawyer Luigi Conti visited his client at the Regina Coeli prison in Rome and said that his client was shocked by the latest development.
Mr Conti said he is still attempting to have Mr Belling released on bail and to be allowed to stay in an apartment in the city instead.
An attempt earlier this month was quashed by a judge involved in the case.
Mr Belling has repeatedly denied involvement in the disappearance of his wife after he was arrested by Italian police at an airport in Rome on February 17.
The family had been on MSC Magnifica since February 9, but Ms Li has not been seen since February 10.