120 people have searched for prisoners in hidden cells or dug-out holes in and around the prison.
The entire building has been searched and analyzed with a scanner, and no living person has been found, says leader Okay Memis.
The oppositional Syrian civil defense group White Helmets has also searched for survivors. They discontinued their operation on early Tuesday, also without finding any living prisoner.
The prison, described by Amnesty International as a "human slaughterhouse", has become a symbol of dictator Bashar al-Assad's brutal regime. Tens of thousands of political prisoners are said to have been executed in extrajudicial mass hangings in notorious Saydnaya. Thousands more are believed to have died due to starvation, torture, and lack of care.
After the fall of the Assad regime, thousands of prisoners were released from the prison.
