Warning: You may find some of the footage disturbing.

Egypt’s jails were one of the most feared parts of former President Hosni Mubarak’s security apparatus – and one of the reasons for the uprising that took place in 2011.

But human rights groups are increasingly documenting a return to some of that period’s worst abuses.

Since July 2013, thousands of Egyptians have been rounded up and jailed – many held without charge or judicial oversight, in prisons where they can face torture and mistreatment.

Inside Egypt’s Prisons is a special investigation by Al Jazeera correspondent Jamal Elshayyal with exclusive interviews with former detainees.