A Turkish man named Faysal Ugar has been held in police custody since September 22 despite lack of an existing detention warrant about him, according to a tweet posted by the man’s brother, Engi Ugar.

“My brother, Faysal Ugar, left yesterday for Friday prayer. They told us that despite lack of a detention warrant, he hes been held at Kahramanmaraş KOM [department of anti-smuggling and organised crime],” Engi Uçar tweeted late on Saturday.

In a following tweet, he said that he is quite worried as the detained brother may face ill-treatment in custody.

Mysterious disappearances involving already-victimized opposition groups have become a common occurrence in Turkey in the aftermath of a July 15 coup attempt.

At least 15 cases of alleged abductions of people who have links to the Gülen group, which is accused by Turkish authorities of being behind a failed coup last year, have occurred in various Turkish cities since July 15, 2016.

Ugar is thought to be taken into custody over his link to the group.

Previously, an accountant, an engineer, three teachers, a lawyer, a university employee, two intelligence agency officials, an Information and Communication Technologies Authority (BTİK) employee and a Competition Authority employee were reported missing. One of the teachers was handed over by unidentified men to police after spending 42 days out of sight.

All have in common in their personal histories that they have lost their jobs amid a sweeping crackdown that the Turkish government has conducted against its critics, particularly members of the Gülen group.

In a parliamentary question for Prime Minister Binali Yıldırım on April 25, Republican People’s Party (CHP) İstanbul deputy Sezgin Tanrıkulu asked why an effective investigation is not being conducted to find these people and who abducted them.

Tanrıkulu also said there is widespread suspicion about the abduction of these people by MİT.