Independent Russian newspaper Novaya Gazeta has published photocopies of documents they say corroborate their earlier investigation into extrajudicial killings in the North Caucasus republic of Chechnya.

The copies of dated photographs feature 67 unaccounted for individuals detained by Chechen security forces between December 2016 and January 2017 as part of a sweeping anti-terror raid.

The dated photographs, which were taken at different Chechen police stations, show 14 individuals the newspaper previously reported had been shot by Chechen security forces on the night of Jan. 25, 2017.

Novaya Gazeta also obtained appeals written to Chechen human rights ombudsman Nurdi Nukhazhiyev by relatives of the victims. In the letters, relatives mention the dates of victims’ detentions, which correspond to the photographs taken at the police stations.

The anti-terror raids lasted at least six weeks and as many as 200 people are believed to have been detained. The number of detainees executed is unclear, but ranges between 27 and upwards of 56, Novaya Gazeta previously reported.

The victims are believed to have been brought to secret prisons, where they were held for several weeks, executed, and buried in unidentified graves.

Chechen authorities have dismissed the disappearances saying a large number of the people involved fled to Syria. According to Novaya Gazeta, relatives of the victims were threatened into signing documents that verified this claim. They were also forced to forfeit passports belonging to their missing relatives.

Novaya Gazeta sent their findings to Russian law enforcement officials in April and said they had yet to receive an official response.