LOS ANGELES (AP) — The second of two defendants accused of using bogus transcripts and ghostwritten essays to help foreigners gain admission to U.S. colleges, allowing the applicants to fraudulently obtain student visas, has surrendered to federal authorities, prosecutors said.

Yi Chen, 33, pleaded not guilty Monday to charges in a 21-count grand jury indictment that alleges conspiracy, visa fraud and aggravated identity theft, the U.S. Attorney’s Office said in a statement.

His co-defendant, Yixin Li, 28, surrendered March 2 and also pleaded not guilty.

The two Southern California men are accused in a scheme to get foreigners into colleges, which allowed them to fraudulently get visas to enter or remain in the United States, prosecutors said.

The indictment alleges that Chen and Li owned so-called educational consulting companies in the southern California cities of Alhambra and Arcadia that charged foreign students thousands of dollars for “guaranteed” admission to a college that would lead to the issuance of an F-1 student visa.

The pair prepared application packages that used fake transcripts and they hired people to impersonate the prospective student to take standardized tests, according to the court documents.

The indictment lists a number of foreign nationals for whom Chen and Li allegedly obtained transcripts, which helped the students gain admission to schools including New York University, Columbia University, Boston College, and several University of California campuses.

Chen was ordered detained pending trial, which was scheduled for May 4. Li remains in custody and his trial is set for April 27.