Police have released the 21-year-old man arrested in connection with the murder of two French students.
"He has been released with no further action," a police spokesman said.
Bio-engineering students Laurent Bonomo and Gabriel Ferez, both 23, were bound, gagged and stabbed over 200 times in Bonomo's apartment in what police said was one of the most "frenzied, brutal and horrific" murders they had seen.
Earlier, the parents of one of the students appealed for the killer to come forward.
"We plead with you to turn yourselves in to the police. You will not be able to live in hiding forever," Mr Ferez's parents, Francoise and Olivier, said in a statement.
"You may be scared and feel like a coward, but you must recognise this terrible mistake you made. Rest assured that we will not leave you in peace."
Mr Bonomo was stabbed nearly 200 times, while Mr Ferez suffered some 50 knife wounds. The apartment was then set on fire.
A black Packard Bell laptop computer was stolen from the flat six days before the murders. Mr Bonomo disturbed an intruder who stole the laptop as he took an early morning shower.
Forensic experts have found no evidence of forced entry after Sunday's murders.
Two Sony handheld games consoles were also taken that day, and credit cards are also believed to be missing.