Actress Lori Loughlin and her fashion designer husband were among 16 parents involved in the college admissions cheating scam who were indicted by a federal grand jury, which added a money laundering charge to their legal woes, federal authorities announced Tuesday.

The parents, including Loughlin and her husband, Mossimo Giannulli, "were charged today in Boston in a second superseding indictment with conspiring to commit fraud and money laundering in connection with a scheme to use bribery to cheat on college entrance exams and to facilitate their children’s admission to selective colleges and universities as purported athletic recruits," the U.S. Attorney's Office in Boston announced.

Loughlin and Giannulli, who were among a total of nearly three-dozen parents arrested last month on mail-fraud charges in a criminal complaint, are accused of conspiring with scam mastermid William “Rick” Singer, 58, of Newport Beach, Calif., and others, to bribe college officials and coaches, and to artificially inflate entrance exam scores, in order to get their children admitted to elite colleges and universities.

Prosecutors said the second superseding indictment also charges the defendants with conspiring to launder bribes and other payments in connection with the fraud, by funneling them through Singer’s purported charity and his for-profit corporation, as well as by transferring money into the United States, from outside the country, for the purpose of promoting the fraud scheme.

Neither Loughlin nor Giannulli nor their legal team responded to messages from USA TODAY.

A superseding indictment means the original indictment was amended or updated, says James Cohen, a law professor at Fordham University in New York. “Sometimes charges are added or subtracted and other times you have defendants that are added or subtracted,” he said.

The bottom line for Loughlin and the rest: This is as about as good as it’s going to get in terms of a plea agreement, he said. The addition of a money-laundering charge means any defendant hoping to be "within striking distance" of a no-prison sentence will probably be disappointed.

"If you think you’re gonna get down to a guideline range where you’re likely to get probation, forget it," Cohen said. "Or (prosecutors) may say, ‘This is as close as you’re gonna get. You might get probation but we’re not going any lower. In fact, the offers are only going to get worse.' "

Under the usual procedures, the next step for these 16 parents will be to appear at an arraignment where they will enter a plea or guilty or not guilty. Then a trial date would be set by the court.

But even before they are arraigned, the parents could still agree to plead guilty under a plea agreement worked out with prosecutors, as 13 parents did Monday, including actress Felicity Huffman.

The announcement of those plea agreements heightened the pressure on Loughlin and those parents who have not done the same. A federal grand jury indictment, with an additional federal charge added to the tally, further bumps up the pressure.

"This absolutely places pressure on the defendants who have not pleaded," says Adam Citron, a former state prosecutor-turned-defense attorney in New York. "They now see that the window to agree to the plea deal is fast closing...with the risk of a withdrawn plea offer. Presumably any plea deal post-indictment will not be as favorable."

The charge of conspiracy to commit mail and wire fraud and honest services mail and wire fraud provides for a maximum sentence of 20 years in prison, plus hefty fines. The charge of conspiracy to commit money laundering provides for a maximum sentence of 20 years in prison, and even heftier fines.

“The money-laundering charge makes it a more serious offense for anyone who is convicted of it – and that includes guilty pleas,” Cohen says. “The guidelines on money laundering are tougher than just plain fraud.”

He noted that the updated indictment also includes forfeiture allegations, which means prosecutors plan to seize the bribe money allegedly funneled through Singer. “They're looking for money,” Cohen said. “They want to make sure it doesn’t go back to any of these (defendants), and that will be in addition to any fines (imposed)."

He said the government's goal is to make sure these defendants are punished.

“They’ve easily included within that goal punishment by depriving them of any financial reward from this enterprise and they’ve now taken steps to make sure that happens,” Cohen said. “I think the money-laundering forfeiture allegation is the strongest” way to recoup the money.

The prosecutors in Boston were closed-mouthed about the indictments; grand jury proceedings are secret and prosecutors are barred from discussing them.

However, the process prosecutors are following is routine: If someone is arrested and charged with a crime in a criminal complaint, the government then has 30 days to indict.

Duncan Levin, managing partner at the law firm Tucker Levin, and a former federal and state prosecutor and expert in money laundering and fraud law, says it's routine prosecutorial practice to try to induce someone to plead guilty early by threatening to add charges later on. The fact that Loughlin and the others didn't, suggests to him they may have already decided to go to trial rather than enter a plea agreement.

"Put differently, there is a reward for early acceptance of responsibility, and that seems to be what's going on here," Levin said. "The bribery cases are far more likely to result in jail, even without the new charges. What this indicates to me is that the defendants who are having these new charges added have already made up their minds to go to trial."

It's not a coincidence that new charges are being added in cases involving bribery, he said. "I'm sure these charges are being added because the government now knows it has some trials on its hands and want to go in with the full panoply of what it thinks happened," Levin said.

The defendants in the college admissions case, dubbed Varsity Blues by the U.S. Attorney's Office, totaled 50, including 33 parents. Most were arrested in their homes on March 12, appeared at federal courthouses in their home cities and were released on bail. They began making their first appearances in federal court in Boston last week.

Loughlin, 54, and Giannulli, 55, are specifically accused of paying $500,000 in bribes to get their two daughters into the University of Southern California as crew athletes, even though neither were ever crew athletes.

Loughlin is best known for her role as Aunt Becky in the early 1990s sitcom "Full House." Giannulli's Mossimo fashion brand is sold at Target.

Under federal sentencing guidelines, they each could face longer prison terms in the event of conviction or a plea deal because of the high amount they are accused of paying in bribes. The additional conspiracy to commit money laundering charge could add even more time.

Huffman, 56, known to millions from TV's "Desperate Housewives" and for her Oscar-nominated role in "Transamerica," is accused of paying $15,000 to arrange for a test monitor to artificially inflate her daughter's SAT exam scores by correcting her wrong answers.

After the plea agreements were announced Monday, Huffman issued what read like a deeply felt statement of contrition. She said, "I'm ashamed," and apologized to her family, friends, colleagues and to students and their parents who work to get into college without cheating.

"I am in full acceptance of my guilt, and with deep regret and shame over what I have done, I accept full responsibility for my actions and will accept the consequences that stem from those actions," she wrote. "I am ashamed of the pain I have caused my daughter, my family, my friends, my colleagues and the educational community..This transgression toward (my daughter) and the public I will carry for the rest of my life. My desire to help my daughter is no excuse to break the law or engage in dishonesty."

According to a copy of the proposed plea agreement with Huffman posted by the U.S. Attorney's Office in Boston, prosecutors agreed to recommend a sentence of prison time “at the low end” of the federal sentencing guidelines range, meaning months instead of a maximum of 20 years. The plea agreements announced Monday still must be approved by a federal judge.

The other parents indicted with Loughlin and Giannulli include:

Gamal Abdelaziz, 62, aka “Gamal Aziz,” of Las Vegas, Nev.

Diane Blake, 55, of Ross, Calif.

Todd Blake, 53, of Ross, Calif.

I-Hsin “Joey” Chen, 64, of Newport Beach, Calif.

Elizabeth Henriquez, 56, of Atherton, Calif.

Manuel Henriquez, 56, of Atherton, Calif.

Douglas Hodge, 61, of Laguna Beach, Calif.

Michelle Janavs, 48, of Newport Coast, Calif.

Elisabeth Kimmel, 54, of Las Vegas, Nev.

William McGlashan, Jr., 55, of Mill Valley, Calif.

Marci Palatella, 63, of Hillsborough, Calif.

John Wilson, 59, of Lynnfield, Mass.

Homayoun Zadeh, 57, of Calabasas, Calif.

Robert Zangrillo, 52, of Miami, Fla.

Three other parents — David Sidoo, 59, of Vancouver, Canada; Gregory Colburn, 61, of Palo Alto, Calif.; and Amy Colburn, 59, of Palo Alto, Calif. — were previously indicted in connection with the scheme.

Contributing: Jayme Deerwester