Three Los Angeles residents were arrested Wednesday after federal officials accused them of operating four schools that helped foreign nationals stay in the United States as students without attending classes.

Three of the schools, Prodee University/Neo-America Language School, Walter Jay M.D. Institute and the American College of Forensic Studies, were located in Koreatown. The fourth, Likie Fashion and Technology College, is in Alhambra, according to the U.S. Attorney’s Office in Los Angeles.

The three defendants are Hee Sun Shim, 51, of Beverly Hills, the owner and manager of the schools, and school employees Hyung Chan Moon, 39, and Eun Young Choi, 35, both of Los Angeles. They were named in a 21-count indictment by a federal grand jury.

They are accused of conspiracy to commit immigration fraud, money laundering and other immigration offenses. Under the indictment, the three would also have to pay back money and return property associated with the schools, which possibly took in up to $6 million a year in tuition fees, according to investigators.

All three defendants are expected to make a court appearance on Thursday. School representatives did not immediately return calls for comment.