Turkish police detained Friday 57 former employees of Borsa Istanbul -- Turkey's main stock exchange -- as part of a probe into the Fetullah Terrorist Organization (FETO).
The suspects, who were arrested in simultaneous operations in six provinces including Istanbul, Giresun, Balikesir, Bursa and Kayseri, are among the 102 suspects against which arrest warrants were issued by the Istanbul chief public prosecutor's office, according to a police source, speaking on condition of anonymity due to restrictions on speaking to the media.
The suspects are accused of "being members of a terrorist organization", with some blamed for using the ByLock messaging app which is said to have been used by members of FETO during the July 15 coup attempt, the source said.
Operations are ongoing to arrest the remaining 45 suspects.
The ByLock smartphone app is believed to have been cracked by Turkish security agencies months before the coup, allowing them to identify tens of thousands of apparent FETO supporters.
The government said U.S.-based FETO leader Fetullah Gulen masterminded the failed coup, which left 249 people martyred and nearly 2,200 injured.
Ankara accuses FETO of being behind a long-running campaign to overthrow the state through the infiltration of Turkish institutions, particularly the military, police and judiciary.
In the wake of the coup attempt, tens of thousands of FETO suspects have been arrested, including many in the armed forces, police, justice system and education sector.