Ms Huffman and Ms Loughlin were due to appear in Federal Court in Los Angeles later on Tuesday, prosecutors said.
Among the alleged offences: six-figure bribes paid to college athletic coaches to vouch for applicants who may not have even competed in those sports, the use of stand-ins to take the all-important SAT and ACT entrance exams, and payments directed to test administrators to correct answers before submission.
"This case is about the widening corruption of elite college admissions through the steady application of wealth combined with fraud", Lelling said Tuesday.
Several colleges have already released their statements claiming they were "victims" of the bribery scheme, Fox News reported earlier.
Thirty-three parents, including actor Lori Loughlin, were charged, as well as 13 coaches and associates of Singer's business.
He is accused of paying $200,000 to have someone else take his two sons' SATs in order to help get them into elite colleges.
Prosecutors said that on a call with one parent, Singer summed up his business thusly: "What we do is help the wealthiest families in the USA get their kids into school ... my families want a guarantee".
Following the arrest, Deadline reports the actress has been released on bail having to pay a $250,000 bond and surrendering her passport whilst also staying at the Los Angeles courthouse for the time being. She is expected to appear in court in Boston on March 29.
Loughlin, of Full House fame, and Huffman, whose credits include the hit ABC show Desperate Housewives, are charged with conspiracy to commit mail fraud and honest services mail fraud. Macy was not charged; authorities did not say why.
Loughlin and Giannulli allegedly paid a total of $500,000 so that their two daughters would be designated as recruits to the University of Southern California's crew team, though neither girl participated in the sport.
Prosecutors said the scheme began in 2011 and also helped children get into the University of Texas, Georgetown University, Wake Forest University and the University of California, Los Angeles (UCLA).
The colleges themselves are not targets, the prosecutor said.
Stanford's sailing coach John Vandemoer pleaded guilty Tuesday in Boston.
Three other cooperating witnesses, including a former head coach of women's soccer at Yale, have agreed to plead guilty, prosecutors said.
In the meantime, many other celebs have taken to social media to either criticise and condemn the parents or roast them over the scandal.