Nine days after launching a virtual museum that documents crimes by the Assad regime against prisoners, activist and journalist Amer Matar was arrested and confined overnight by Syrian authorities.

Matar was arrested on Wednesday at a border crossing between Syria and Lebanon for allegedly “illegally” obtaining documents belonging to security services and exploiting them for personal use, according to Ministry of Interior spokesperson Noureddine Al-Baba. Al-Baba said Matar was previously summoned by authorities, but he ignored the order and attempted to leave the country, an allegation Matar’s museum denied in a statement.

He was reportedly released on bail on Thursday after an investigation found that the documents in his possession did not warrant his detention.

On Sept. 15, Matar launched the Syria Prisons Museum, a virtual museum dedicated to uncovering crimes in prisons under former President Bashar al-Assad’s regime and preserving the memory of those who were unjustly detained — the whereabouts of hundreds of thousands of whom are still unknown, according to official estimates. In addition to a 3D tour of the notorious Sednaya Prison and testimonies by former prisoners, the virtual museum features documents that describe inmate numbers, movements and deaths.

Hours after his release, Matar responded on social media to claims that he stole records, writing, “What we did is exactly what thousands of families of the missing have done: attempting to photograph what we could before the chaos destroyed them — identities of detainees and documents related to their detention and lives inside prisons.”

Matar also called on Syrian authorities to provide clear instructions on dealing with documentation from the former regime “so that what happened to me is not repeated.”

Sources at the museum told The New Arab that the museum sends any original records they find to the National Commission for the Missing, a government body charged with investigating the fate of people who were disappeared by the Assad regime.

“It is committed to protecting these documents from loss or damage, given their value in revealing the fates of victims and preserving Syrian memory,” the museum wrote in a statement.

Matar was previously arrested by Syrian security forces in 2011 and imprisoned for eight months in Al-Khatib, a prison infamous for torture, where he said he was subjected to beatings by cables and whips. In 2022, his testimony in a German court led to the first torture conviction against a member of Assad’s forces, former colonel Anwar Raslan. Raslan is now serving a life sentence.

Matar’s most recent arrest took place as Syrian President Ahmed al-Sharaa became the first Syrian president in nearly 60 years to address the United Nations General Assembly.

“I guarantee to bring to justice everyone accountable and responsible for bloodshed,” he said on Wednesday. He highlighted his government’s transitional justice efforts and called on world leaders to lift sanctions against Syria.