The Judea and Samaria Police, along with the immigration police, apprehended 25 illegal immigrants from Turkey and China in a joint operation overnight Wednesday.
Five of the workers were caught in Alon Moreh - three of whom were employed in a leather factory that prepares parchment for mezuzot.
The other 20 were found in Har Bracha, working in construction.
The detainees were taken for investigation by immigration officials.
Cases will be brought against their employers in the near future, Judea and Samaria Police said.