Six people have been charged in the case and four of them have been placed in pre-trial detention, officials said during a news conference in the northern city of Olsztyn.
The suspects face accusations including participation in an organised crime group, document forgery and facilitating the illegal stay of foreigners in Poland.
Authorities described the case as the largest of its kind uncovered recently in the northeastern Warmia-Masuria region.
According to regional police chief Mirosław Elszkowski, the scheme involved entrepreneurs from the Iława area who he said used fake certificates confirming that foreigners had begun studies at universities in the capital Warsaw and the Baltic city of Gdańsk.
The documents allowed companies to bypass regulations governing the employment of foreign workers.
Investigators began looking into the case late last year after suspecting irregularities at a company that mediated employment for foreigners in local businesses.
Six suspects aged between 21 and 49 were detained in the investigation.
A district court in the town of Iława ordered four of them held in custody for three months at the request of prosecutors, while the other two were placed under police supervision.
If convicted, they face up to eight years in prison.
During the investigation, officers inspected nearly 200 foreign nationals, 16 accommodation sites and 15 workplaces.
Authorities found that 105 foreign workers had been employed illegally.
Most of them were Colombian nationals, but the group also included citizens of Cuba, Venezuela, Guatemala, Moldova and Ukraine, said Brig. Gen. Daniel Wojtaszkiewicz, head of the Warmia-Masuria Border Guard unit.
Some of the foreigners lacked a secondary school diploma, officials said, which further indicated that the documents claiming they had enrolled in university studies were forged.
Border Guard officers have launched administrative proceedings against the 105 foreigners ordering them to return to their home countries.
Three Colombian nationals who lacked valid entry and residence documents have already received orders to leave Poland.
Authorities said the investigation is ongoing and further detentions are possible.