Last weekend investigators from the Department of Immigration and Emigration raided a factory in the Kalutara district and arrested seven Indian nationals.
The Controller of Immigration and Emigration P B Abeykoon says the raids will continue.
They did not have valid work permits.
Though foreign firms operating in Sri Lanka can legally employ foreign workers, they sometimes exceed permitted quota.
Indian nationals get visas on arrival in this country.
Officials estimate that there are around 3000 to 4000 foreign workers illegally working in Sri Lanka mainly of Indian origin, who arrived in the country using tourist visas.
Last month the department deported several commercial sex workers of Eastern European origin who were in Sri Lanka on tourist visas.
Immigration Officer Upali Tennakoon from the Immigration Department™s investigation section says many foreign factories are employing persons who arrive in the country on tourist visas.
The factory that was