Authorities have determine that Osman Karaca, the so-called "imam" of Mexico for the Gülenist Terror Group (FETÖ), used ByLock, an encrypted messaging app developed and used exclusively by the terrorist group.

Senior officials had announced on Saturday that Karaca was arrested by the Turkish National Intelligence Organization (MİT) in Cambodia and brought to Turkey. In police custody, Karaca will be interrogated for the next few days in Istanbul as prosecutors work to finalize an indictment against him.

He was arrested on charges of ''founding and masterminding an armed terrorist organization,'' said a government source, who asked not to be named due to restrictions on speaking to the media.

The ByLock app was detected on nine different phone lines that are registered to Karaca’s name.

Officials determined in investigations led by the Gaziantep, Istanbul and Ankara chief public prosecutors, that the FETÖ member was using the ByLock app.

Many arrests have occurred in the scope of the investigations into FETÖ’s international reorganization, and many critical suspects have been captured and brought back to Turkey.

The MİT's latest operation that they have conducted with various security forces all around the world took place in Cambodia this past week.

The MİT mobilized following the arrest warrants issued on Karaca, and determined that he had traveled to Cambodia using a fake passport. He was arrested in a bank in the capital city of Phnom Penh, following "return" negotiations conducted with the Cambodian security forces.

After his arrest on Oct. 14, he was held under arrest for some time then brought back to Turkey by MİT agents.

FETÖ and its U.S.-based leader Fetullah Gülen orchestrated a failed coup on July 15, 2016, which left 251 people dead and nearly 2,200 injured.

Ankara accuses FETÖ of being behind a long-running campaign to overthrow the state through the infiltration of Turkish institutions, particularly the military, police and judiciary.

FETÖ is blamed for planting its members everywhere, from the police to the judiciary, the army and bureaucracy, for years. Disguising their ties to the group, followers managed to rise to the top ranks. They became generals in the army and senior police chiefs.

Through its "imams," FETÖ monitored its infiltrators and gave them orders. These so-called imams are often unassuming figures, such as a shopkeeper in a small town or a teacher, but they held immense power in the group, sometimes over police chiefs, generals and high-ranking bureaucrats.