Rescue teams and relatives of disappeared people in Syria are searching for their loved ones at the notorious Sednaya Prison in Damascus after the fall of President Bashar al-Assad’s government.

An intense search was under way at the jail on Monday for “hidden underground cells, reportedly holding detainees”, said the White Helmets rescue group, which dispatched emergency teams to the facility.

Al-Assad’s police state was known for generations as one of the harshest in the Middle East, holding hundreds of thousands of political prisoners.

Bewildered and elated prisoners poured out of Syrian jails on Sunday as al-Assad’s government collapsed. They shouted with joy as they emerged from one of the world’s most notorious detention systems.

Throughout Syria’s war, which began in 2011, security forces held hundreds of thousands of people in detention camps where international human rights organisations said abuses were rampant. Families were often told nothing of the fate of their loved ones.

As rebels seized one city after another in a blistering eight-day campaign, prisons were often among their first objectives. The most notorious prisons in and around Damascus itself were finally opened on the uprising’s final night and the early hours of Sunday.

All across Syria, families wept as they were reunited with children, siblings, spouses and parents who vanished years ago into the impregnable gulag of the al-Assad dynasty’s five-decade rule.