At least 17 teachers who were earlier dismissed from their jobs over links to the Gulen movement, were detained over similar charges on Tuesday.
Police carried out operations in Bursa, İstanbul, Tekirdağ, Kütahya and Balıkesir provinces to detain 21 teachers for whom a Bursa prosecutor issued arrest warrants as part of an investigation into the movement.
Turkish government accuses the movement of masterminding the July 15, 2016 coup attempt while the latter denies involvement.
17 teachers have been rounded up so far as police have yet to locate the remaining 4.
Meanwhile, 8 shopkeepers were also detained as part a separate, Ankara-based investigation into the movement the same day.
In another operation in Antalya, police caught 11 people working for a preparatory school in Aksu district on Tuesday.