BOSTON — Federal prosecutors on Tuesday brought new charges against 11 parents and seven others who continue to maintain their innocence in the nation's college admissions scandal, raising the prospect for potentially longer prison sentences if they are convicted.

Among the parents hit with a new bribery charge are actress Lori Loughlin and husband fashion designer Mossimo Giannulli, who are accused of paying $500,000 to get their two daughters falsely classified as crew recruits to be admitted into the University of Southern California.

The moves come after four parents charged in the admissions scheme pleaded guilty in Boston federal court Monday, choosing to admit guilt rather than face an additional federal programs bribery charge prosecutors threatened to bring.

In addition, prosecutors brought new fraud conspiracy charges against seven others, including four former college coaches, who have pleaded not guilty to racketeering charges in the scam. Three of the defendants, each former university athletics employees, also have been charged with conspiracy to commit bribery against a program that takes federal money.

More:Third parent in 24 hours caves in college admissions scandal, agrees to plead guilty

Charges are outlined in superseding indictments returned by a grand jury in Boston federal court. For the parents, it adds to the fraud and money laundering charges they already face for paying Rick Singer, the mastermind of the scheme.

The new charges do not allege new actions. Prosecutors are looking to ramp up pressure against the remaining 23 parents, coaches and other defendants who have not caved and are preparing for trial in the "Varsity Blues" case.

"Today's charges are the result of ongoing investigation in the nationwide college admissions case," U.S. Attorney Andrew Lelling said in a statement. "Our goal from the beginning has been to hold the defendants fully accountable for corrupting the college admissions process through cheating, bribery and fraud."

The federal programs bribery statute involves theft or bribery from entities that receive at least $10,000 in federal funding, such as universities. Prosecutors argue the 11 parents conspired to bribe employees of USC to facilitate their children's entry as fake athletic recruits.

Other parents facing the new charge are Gamal Abdelaziz; Diane Blake; Todd Blake; Elisabeth Kimmel; William McGlashan Jr.; Marci Palatella; John Wilson; Homayoun Zadeh; and Robert Zangrillo.

William Trach, Loughlin and Giannulli's attorney, did not respond to a request for comment.

The government also brought additional charges of wire fraud and honest services wire fraud against four parents: Joey Chen, McGlashan, Wilson and Zangrillo.

Martin Weinberg, Zangrillo's attorney, called the new bribery charge an "unprecedented attempt to criminalize a donation made to a University by a parent."

"Mr Zangrillo is not guilty of each and every one of today's allegations," Weinberg said in a statement.

Fifty-two defendants are charged with crimes in the admissions case, first announced in March. They include 35 parents accused of paying Singer significant bribes to either facilitate cheating on their children's college entrance exams or tag their children as athletic recruits to get them into school. Twenty-nine defendants, included 19 parents, have since pleaded or agreed to guilty.

The four parents who pleaded guilty Monday — Douglas Hodge, Michelle Janavs and Manuel and Elizabeth Henriquez — told a judge that in exchange for their pleas, no new additional charges would come their way.

“If the court accepts my plea, the government has promised not to seek or bring additional charges against me," Manuel Henriquez, founder and CEO of the venture capital firm Hercules Capital, said prior to pleading guilty.

More:Felicity Huffman reports to prison to begin serving time in college admissions scandal

If convicted of federal programs bribery, parents could be subject to lengthier prison terms based on federal guidelines that judges consider during sentencing. The crime carries a maximum penalty of five years in prison. Fraud and money laundering each carry a maximum of 20 years in prison.

Parents who pleaded guilty months ago were sentenced in recent weeks. Although nine of 10 received prison, U.S. District Judge Indira Talwani has rejected the government's push to use bribe amounts paid to Singer as a reason to give parents longer prison sentences.

As a result, no parent has gotten more than five months in prison. Parents involved in cheating on the ACT or SAT received one month or less in prison. Actress Felicity Huffman reported to a federal prison in Dublin, California, last week for a 14-day sentence for paying Singer $15,000 to have someone correct answers on the SAT of her oldest daughter.

The seven other defendants who face new charges are USC's former senior associate athletics director Donna Heinel; former Georgetown tennis coach Gordon Ernst; former UCLA soccer coach Jorge Salcedo; former Wake Forest University volleyball coach William Ferguson; former USC water polo coach Jovan Vavic; Mikaela Sanford, who was employed by Singer's sham nonprofit; and Niki Williams, a former test administrator for the ACT and SAT exams.

Each is charged with conspiring to commit mail and wire fraud, and honest services mail and wire fraud on top of racketeering charges they already faced. In addition, six have been charged with wire and honest services wire fraud charges. Ernst, Heinel and Salcedo also were charged with the federal programs bribery charge.

The new charges for the alleged Singer co-conspirators come after Martin Fox, president of a private tennis academy in Houston who worked as a middleman for Singer, pleaded guilty to racketeering charges, avoiding any new charges.

“Martin is a good man who deeply regrets getting into this," Fox's attorney, Michael Pineault, said in a statement. "He takes full responsibility for his conduct."

Reach Joey Garrison on Twitter: @joeygarrison.