(CNN) — Actresses Lori Loughlin and Felicity Huffman are among 15 people expected to appear Wednesday in federal court in Boston as part of the college admissions scam.

The defendants are each charged with conspiracy to commit mail fraud and honest services mail fraud in a scheme that prosecutors have called “Operation Varsity Blues.” Authorities say the parents paid a college prep business to cheat on standardized tests and/or bribe college coaches to help get their children into competitive universities.

Several brands have distanced themselves from “Full House” actress Loughlin and her daughter, 19-year-old social media influencer Olivia Jade Giannulli, since the charges were announced.

Loughlin’s husband, the fashion designer Mossimo Giannulli, is also expected to appear in court Wednesday. Huffman’s husband, the actor William H. Macy, is not charged in the case.

CNN has reached out to representatives for Huffman, Loughlin and Giannulli but has not heard back.

Of the 50 people charged in the case, four have pleaded guilty or plan to plead guilty, according to prosecutors.

Rick Singer, the mastermind of the scheme; Rudy Meredith, the Yale University women’s soccer coach who accepted a bribe to help a student get admitted; and Mark Riddell, who cheated for the students on the SATs and ACTs, are all cooperating witnesses for the prosecution. They have agreed to plead guilty and testify for the prosecution in exchange for lesser sentences.

John Vandemoer, Stanford University’s former sailing head coach, has also pleaded guilty to conspiracy to commit racketeering.

Stanford, the University of Southern California, Georgetown University and other schools implicated in the scheme have said they are reviewing the admissions of students accused of participating. Last week, Yale rescinded the admission of one student whose family had allegedly paid $1.2 million to gain entry under false pretenses.

What the complaint says

Loughlin and Huffman are the best-known figures in the scandal, and the accusations against them explain how the admissions scam allegedly worked.

Huffman is accused of paying $15,000 to a fake charity associated with Singer to facilitate cheating for her daughter on the SATs, the complaint says. She discussed the scheme in a recorded phone call with Singer, the complaint says.

Separately, Loughlin and Giannulli allegedly agreed to pay bribes totaling $500,000 in exchange for having their two daughters designated as recruits to the USC crew team, easing their acceptance to the school.

The daughters were recruited as coxswains even though they did not row competitively or otherwise participate in crew, the complaint says. The parents even sent Singer photos of each of their daughters on an ergometer, the rowing machine, the complaint states.

“I wanted to thank you again for your great work with (our older daughter), she is very excited and both Lori and I are very appreciative of your efforts and end result!” Giannulli allegedly wrote in an email to Singer included in the complaint.

Additional arrests are expected as the investigation continues, a law enforcement official familiar with the probe told CNN last week.

Investigators are expecting to charge more than five others within four to six weeks, according to the official, who cautioned the investigation is ongoing and this is subject to change.

Correction: The number of people scheduled to appear Wednesday in federal court in the college admissions scam is 15, not 11 as reported earlier.

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