Turkish prosecutors in Kayseri and Adıyaman provinces have issued arrest warrants for at least 64 people on accusations that they use a smart phone application known as ByLock, the state-run Anadolu news agency reported on Thursday.

According to the report, warrants were issued for 24 people in Kayseri, and 13 of them were detained as part of an investigation into the Gülen group, accused by the Turkish government of mounting a coup attempt last summer.

Police detained 32 of 40 people during operations in Adıyaman, Ankara, Kahramanmaraş, Şanlıurfa, Hatay, Gaziantep and Nevşehir on Thursday, in an Adıyaman-based investigation into the Gülen group.

On Wednesday, police detained 16 of 32 people in Samsun province, part of a probe of the movement.

Turkish authorities believe using ByLock is a sign of being a Gülen movement member as they see the mobile phone application as the top communication tool among the group.

Tens of thousands of civil servants, police officers and businessmen have either been dismissed or arrested for using ByLock since a failed coup attempt on July 15, 2016.

Turkey survived a military coup attempt on July 15 that killed 249 people and wounded more than a thousand others. Immediately after the putsch, the Justice and Development Party (AKP) government along with President Tayyip Erdoğan pinned the blame on the Gülen movement.

Fethullah Gülen, the leader of the group, repeatedly denied having any role in the failed coup, but President Erdoğan and his government initiated a widespread purge aimed at cleansing sympathizers of the group from within state institutions, dehumanizing its popular figures and putting them in custody.

Turkey’s Justice Ministry announced on July 13 that 50,510 people have been arrested and 169,013 have been the subject of legal proceedings on coup charges since the failed coup.

Turkey has also suspended or dismissed more than 150,000 judges, teachers, police and civil servants since July 15.