Four state Registry of Motor Vehicle clerks and two other people have been charged with conspiring to help illegal immigrants get false identifications — some of which were used to register to vote in Boston — in a blockbuster bust that state officials call “troubling and intolerable.”

The clerks, who were employees at the RMV’s bustling Haymarket Service Center, have been placed on administrative leave without pay pending further review. All six were arrested yesterday and made their initial appearances at Boston’s federal courthouse.

“The RMV finds the alleged criminal and fraudulent actions of these individuals to be troubling and intolerable and has also taken immediate steps to suspend the credentials allegedly fraudulently obtained as part of this enterprise,” Erin Deveney, the registrar of the RMV, said in a statement.

Evelyn Medina, 56, of Boston; Annette Gracia, 37, of Boston; Kimberly Jordan, 33, of Randolph; David Brimage, 46, of Boston; Bivian Yohanny Brea, 41, of Boston; and a 32-year-old man identified as John Doe — who goes by “Flako,” among other aliases — were arrested for their role in the alleged scheme.

Medina, Gracia, Jordan, and Brimage were employed as clerks at the Haymarket Registry of Motor Vehicles, according to authorities. Brea and Flako, meanwhile, conspired with the RMV clerks to operate the scheme, federal prosecutors say.

Flako, who according to authorities is an illegal immigrant from the Dominican Republic, was the only person held after yesterday’s hearing. When he was arrested, he had a fake green card, according to prosecutors. U.S. Immigration and Customs Enforcement has a detainer on Flako, according to federal authorities.

“His role in the scheme caused a number of false Massachusetts identifications and licenses to be issued, as well as false voter registrations,” said Assistant U.S. Attorney Eugenia M. Carris. “His role was the document dealer.”

Carris said federal authorities have notified the secretary of state’s office about the illegal voter identities that were obtained. State authorities said they have no evidence that anyone voted illegally.

“Based on the limited information provided by the U.S. Attorney’s Office, it appears that none of these individuals have voted,” Debra O’Malley, spokeswoman for the secretary of state, said in an email.

The RMV indicated that it already has taken steps to immediately suspend the licenses of those who ­received them.

State police began investigating the scheme in 2015 after receiving an anonymous letter alleging that there was a corrupt RMV worker giving out stolen ID cards and driver’s licenses.

The investigation revealed that Medina, Gracia, Jordan, and Brimage were allegedly working with Brea, who acted as the document vendor, and Flako, authorities say.

Prosecutors say Flako on one occasion sold a Puerto Rican birth certificate and U.S. Social Security card to Brea for roughly $900. Brea turned around and sold the stolen identities for thousands of dollars, according to authorities.

Brea would use the counterfeit documents and false identities and addresses to fraudulently register her clients to vote in Boston, prosecutors say. Then, Brea and the client would bring the identification to the Haymarket RMV, where either Medina, Gracia, Jordan or Brimage would ­accept cash to issue authentic RMV documents, including Massachusetts licenses and ID cards, authorities allege.