Turkish authorities have identified some 900 suspects as they investigated Gülenist Terror Group's (FETÖ) infiltration of the Turkish defense giant, ASELSAN.

Authorities had already detained several suspects in earlier operations at the firm, which is behind some of Turkey's most prominent defense projects. FETÖ, run by former preacher Fetullah Gülen, is behind the July 15, 2016 coup attempt. Gülen had instructed his followers to "get into the veins of the state," and thus the terrorist group is known for its widespread infiltration of Turkey's law enforcement, military, judiciary and bureaucracy.

FETÖ's military infiltrators, in the face of an imminent crackdown, moved to topple the government in a coup on July 15, 2016. The attempt was foiled thanks to a strong popular resistance. Turkey initiated a large-scale crackdown on the group following the coup, investigating infiltrations and detained or arrested thousands.

An investigation by the Ankara Chief Prosecutor's Office sought to uncover FETÖ's infiltrators in ASELSAN and ROKETSAN, another major defense firm.

A chief engineer, who worked on the production of ROKETSAN's guided missiles, had confessed his ties to the terrorist group. He cooperated with the authorities to uncover a larger network of infiltrators as well as FETÖ's point men in charge of them.

In the ASELSAN probe, authorities initially identified some 25 suspects. Sifting through intercepted text messages and phone calls of FETÖ-linked suspects detained earlier and with the help of information provided by former FETÖ members, investigators were able to identify as many as 900 suspects in ASELSAN. Some of them were already dismissed from their jobs or suspended for possible links to the terrorist group. More police operations were expected to capture any remaining FETÖ infiltrators in the company soon.

The 25 suspects detained earlier in the probe are accused by prosecutors of leaking confidential information about the defense projects to FETÖ members. Some of the suspects were working on the development of encrypted software for the Turkish Armed Forces. Prosecutors also accused some suspects of deliberately slowing down national defense projects.

FETÖ also faces the accusations of covering up a string of suspicious deaths of ASELSAN employees, including engineers working on critical defense projects.

At least eight former and serving ASELSAN employees died in accidents or suicides over the past decade but each case was closed despite objections from their families, who claimed foul play. Two former prosecutors who handled and closed the cases of the deaths are now charged with FETÖ membership.

The terrorist group had disguised itself as a charity with religious undertones for decades and is known for its widespread infiltration of the military, judiciary, law enforcement and bureaucracy. When the government moved to weed out what it called "a parallel state" of Gülenists from those institutions, the group moved to seize power. In 2013, it tried to topple the government through its infiltrators in the police and judiciary. Investigations after the 2013 attempts revealed the group was involved in an array of crimes, from money laundering to illegal wiretapping, as well as sham trials used to stifle the group's critics.