The UN investigative body for Syria says it is possible "more than enough" evidence will be found to convict people of crimes under international law.
Syria's prisons were opened after an Islamist-led rebel alliance ousted longtime ruler Bashar al-Assad this month.
The fall of the regime came more than 13 years after Mr Assad's brutal repression of anti-government protests triggered a war that killed more than 500,000 people.
With families rushing to former prisons, detention centres and alleged mass graves to find any trace of disappeared relatives, many have expressed concern about safeguarding documents and other evidence.
Robert Petit heads the International Impartial and Independent Mechanism (IIIM) set up by the UN in 2016 to prepare prosecutions for major international crimes in Syria.
He said the IIIM may find "more than enough evidence left behind to convict those" that should be prosecuted.
Mr Petit added that preserving evidence would "need a lot of coordination between all the different actors".
"We can all understand the human impulse to go in and try and find your loved ones," he said.
"The fact is, though, that there needs to be a control put in place to restrict access to all these different centres … it needs to be a concerted effort by everyone who has the resources and the powers to do that to freeze that access, preserve it."
Steps towards prosecution
The organisation, known as the Mechanism, was not permitted to work in Syria under Mr Assad's government but was able to document many crimes from abroad.
Mr Petit has been able to visit the country since Mr Assad's fall, but his team still requires authorisation to begin the work inside Syria that it had requested.
He said his team had documented hundreds of detention centres and every security centre, military base and prison "had their own either detention or mass graves attached to it".
"We're just now beginning to scratch that surface and I think it's going to be a long time before we know the full extent of it," he said.
According to the Syrian Observatory for Human Rights monitor, more than 100,000 people died in Syria's jails and detention centres from 2011.
The Mechanism aims to establish a national accountability process in Syria and that steps could be taken to finally grant the International Criminal Court jurisdiction to prosecute crimes committed in the country.
Weapons to come under state control
Syria's new leader Ahmed al-Sharaa on Sunday said weapons in the country, including those held by Kurdish-led forces, would come under state control.
During a press conference with visiting Turkish Foreign Minister Hakan Fidan, Mr Sharaa said Syria's armed "factions will begin to announce their dissolution and enter" the army.
"We will absolutely not allow there to be weapons in the country outside state control, whether from the revolutionary factions or the factions present in the SDF area", he said, referring to the Kurdish-led Syrian Democratic Forces.
He said the new government was "working on protecting sects and minorities from any attacks that occur between them" and from "external" actors exploiting the situation "to cause sectarian discord".
He also said his administration would announce the new structure of the defence ministry and military within days.
ABC/wires
