The woman was last seen leaving a party about 2 am on New Year's Eve and was reported missing by her mother on Monday, police said.
Passersby found several packages of body parts under the bridge where Ritter-Brüning-Straße crosses the Ihme River on Monday afternoon.
After combing through the current list of missing people, police established the body parts probably belonged to the 24-year-old, though an autopsy on Wednesday would provide certainty, a Hannover police spokesman said.
She had from time to time worked as a street prostitute in the centre of Hannover. Police are urgently seeking witnesses who saw anyone acting suspiciously in the area, any conspicuous cars parked around the bridge or anyone carrying a heavy object.
Anyone with information is asked to call Hannover's crime task force on (0511) 109 5555.