An Istanbul judge Wednesday ordered that 30 lawyers detained as part of a Fetullah Terrorist Organization (FETO)-linked probe be remanded in custody, according to judicial sources.

According to the sources, who asked not to be named due to restrictions on speaking to the media, the group includes Nuri Polat, the counsel for former opposition Nationalist Movement Party (MHP) deputy and chair candidate Meral Aksener; Erdogan Soruklu, the counsel for Erhan Tuncel, accused in the 2007 murder of Turkish-Armenian journalist Hrant Dink; as well as Nazif Aktas and Seyfettin Dayan, who have represented FETO-linked ex-police commissioners.

As part of an investigation into FETO-linked lawyers, 38 suspects initially gave testimony to the Istanbul Chief Public Prosecutor's Office.

The Istanbul judge then ordered the 30 lawyers remanded in custody and the release of the other eight.

The investigation found that 25 of the suspects had used the ByLock mobile app, a suspected means of communication for FETO members. Five of the others had made calls to people who used the app.

According to the Turkish government, FETO and its U.S.-based leader Fetullah Gulen orchestrated the defeated coup of July 2016, which left 249 people martyred and nearly 2,200 injured.

Ankara has said FETO is behind a long-running campaign to overthrow the state through the infiltration of Turkish institutions, particularly the military, police and judiciary.