A laborer walking in the area found a leg belonging to 17-year-old Cara Marie Burke on Sunday, a week after her torso was discovered in a suitcase near a different river. Police searching in the same area Monday found her forearms and head.
Inspector Carlos Raimundo Batista says he is confident the body parts are Burke's.
Police say Mohammed D'Ali Carvalho dos Santos, 20, confessed he dumped Burke's head and limbs into the river.
Last week, Santos said he does not remember what happened the night she died.
In an interview from his jail cell with The Associated Press, Santos said: "I don't remember much, I had used too much drugs."
Santos did not say whether he killed her during the brief interview. Police say Santos has already admitted to killing Burke because she threatened to tell the suspect's parents he was a drug dealer and addicted to cocaine.
Authourities said Friday they are looking for another suspect who helped Santos get rid of Burke's head and other body parts.