Police launched an operation early Friday to capture FETO suspects for their involvement in July 15 deadly coup attempt.
According to police sources, all of the suspects were using the ByLock smartphone app, developed and used by coup plotters.
Istanbul Chief Prosecutors' office, which has been investigating FETÖ terror groups and coup probe, found that 166 personnel from Istanbul Police Department, including former police chief and commissioners, had been using the encrypted app for internal discussion about the coup plan.
The July 15 attempted coup was the deadliest coup attempt in Turkish history.
More than 240 people were martyred by the coup plotters when they fired at pro-democracy demonstrators on the coup night with tanks, combat helicopters and fighter jets in Ankara and Istanbul.
Fetullah Gülen, the U.S.-based leader of the FETÖ terror group was the mastermind of the coup attempt.
Ankara urged Washington to begin his extradition to Turkey as the Turkish Justice Ministry has sent a huge number of dossiers of his orchestration of the coup.