Moscow police detained more than 1,600 immigrants who had been living and working at a construction site in western Moscow.
Fifty-nine immigrants, natives of Central Asia and Turkey, have been charged with violation of entry rules. Deportation hearings against 15 of them will be held soon, the police said in a statement.
Police said that the construction firm had given the unregistered migrants residence at the site since June 2013.
The head of construction firm has been charged with "organizing illegal migration." More than 300 such cases have been opened this year in Moscow, Interfax reported. If convicted the accused could face a five-year prison sentence.
The firm itself will face various small fines under the Administrative Code.
Police also said they would check if anyone of the migrants detained on Friday have committed crimes in Russia.
Moscow prosecutor Sergei Kudeneyev said Friday that half of all crimes in Moscow in the first six months of this year had been committed by foreign citizens, primarily by natives of other former Soviet Union countries.