In a statement, the national prosecutor's office said the suspects were two Iraqi men, aged 22 and 27, one Iranian man, 19, and one Dutch woman, 27. Their names were not released.
The four are suspected of involvement in a ring responsible for two incidents in recent months when 31 illegal immigrants were discovered in the backs of trucks bound for England.
"The organization of the human smuggling was presumably in the hands of a group of Iraqis," the statement said. "They operated by smuggling illegal passengers inside trucks in the cargo hold of a ferry boat."
The suspects were arrested Wednesday and brought before a judge Friday.
The British Prime Minister cuts a sociopathic figure, isolated, stubborn beyond belief, totally wrong and convinced that the world gravitates around her feet
The Basmanny Court of Moscow arrested Michael Calvey, the founder of Baring Vostok investment fund, on allegations of embezzling 2.5 billion rubles from Vostochny Bank. Calvey will be held in custody until April 13