A rebel military spokesman says rebels have freed more than 10,000 from Muammar Qaddafi's prisons since entering Tripoli last week.
But Ahmed Bani said that some 50,000 people are unaccounted for.
Qaddafi's regime sought to break the uprising that broke out in mid-February by locking up thousands of people. Many have been released, but evidence has emerged that regime forces executed dozens of prisoners as rebels seized the capital.
Bani told reporters in the eastern city of Benghazi Sunday that rebels are still searching for Qaddafi. Rebels say many Qaddafi loyalists have fled to Sirte, headquarters of his tribe and his last major bastion.
Bani says: "We hope that Gadhafi is still in Libya, so we can rid the world of this insect."