The baby is believed to have been thrown from the second floor of the hotel in the 20th arrondissement on Monday morning, the Paris prosecutor's office said in a statement shared with Sky News' US partner network NBC News.
An American woman suspected of throwing her newborn out of a hotel window in Paris, killing the baby, has been detained in the French capital.
"The investigation is under way and the precise circumstances of this tragedy remain to be established," a police source told French magazine Paris Match.
The incident is also being looked into as a possible "case of pregnancy denial", the prosecutor's office said.
Officials said the mother - identified as a US national - was part of a group of young adults travelling in Europe.
