On the eve of the closing day of a federal fraud trial in Minneapolis, a woman drove up in a Mazda to a juror’s home holding a Hallmark gift bag emblazoned with butterflies and flowers. Inside were wads of $100, $50 and $20 bills totaling roughly $120,000.

The juror in the case, in which defendants are charged with using a charity to steal millions of dollars, was not home Sunday night when the unusual package arrived. But a relative of the juror grabbed it, according to an F.B.I. agent’s account.

“This is for Juror 52,” Assistant U.S. Attorney Joe Thompson quoted the woman saying, according to a story in Sahan Journal, an online news organization. “Tell her there will be another bag for her if she votes to acquit.”

When the juror, a 23-year-old woman, got home and learned about the dropped-off cash, she called her local police department, which reported the attempted bribery to federal officials.

On Monday, the juror was dismissed and prosecutors asked the judge for permission to seize the cellphones of the seven individuals on trial as investigators endeavored to learn who orchestrated the apparent attempt to bribe a juror.

That revelation roiled the trial. The defendants are accused of stealing $41 million from government programs meant to feed hungry children, through a nonprofit called Feeding Our Future, during the Covid-19 pandemic. Prosecutors have accused them — and dozens of others — of stealing $250 million by claiming to have served nonexistent meals to nonexistent children.

So far prosecutors have charged 70 people in the case, 18 of whom have pleaded guilty. The government has recovered roughly $60 million by seizing bank accounts, real estate properties and vehicles.

In recent days, defense lawyers for the defendants have argued that their clients provided meals to many needy people during the pandemic. They also have sought to discredit a government witness who was a participant in the scheme and who has cooperated with investigators in hopes of getting a more lenient sentence.

In an application for a search warrant submitted to the court on Monday, Travis Wilmer, an F.B.I. agent, noted that the identities of the jurors were known to the defendants.

“Here, it is highly likely that someone with access to the juror’s personal information was conspiring with, at minimum, the woman who delivered the $120,000 bribe,” Mr. Wilmer wrote. “Indeed, in this case in particular, these defendants and other conspirators used electronic communication, including text messages and emails, to communicate about their illicit activities.”

The current case is the first related to that scandal to come to trial. After six weeks, the trial is nearing its end. Defense lawyers made their closing arguments on Monday, and the jury is now deliberating on the case. In court on Monday, defense lawyers said they were troubled by the allegations, according to accounts from the courtroom.

In response to the revelation, U.S. District Judge Nancy Brasel quizzed the remaining jurors and alternates about whether they had been contacted in a similar way, according to an account from The Star Tribune. All said no, the newspaper reported.

The police in Spring Lake Park, Minn. — where the bribe attempt took place — referred questions to the U.S. attorney’s office.

Judge Brasel ordered on Monday that the defendants turn over their phones to F.B.I. agents who would be trying to find evidence of the origin of the bribe attempt. And after closing arguments wrapped up and the jury was given instructions on its deliberations, at prosecutors’ request, the judge ordered that the defendants be detained.

Judge Brasel also ordered that members of the jury remain isolated from other people during the remainder of the trial, a rare step taken in high-profile cases in which jury tampering is a concern.

Sahan Journal reported that the juror who was the intended recipient of the bribe was not in court on Monday. She appeared to be the sole person of color on the jury, the outlet reported. The seven defendants are Somali immigrants: Abdiaziz Shafii Farah, Mohamed Jama Ismail, Abdimajid Mohamed Nur, Said Shafii Farah, Abdiwahab Maalim Aftin, Mukhtar Mohamed Shariff and Hayat Mohamed Nur.

F.B.I. agents interviewed the juror on Monday morning and took custody of the bag of cash from the Spring Lake Park Police Department. The authorities did not disclose whether they had learned the identity of the woman who delivered the cash.

Bribing a juror is a felony.

David Lillehaug, who served as the top federal prosecutor in Minnesota during the 1990s, said jury tampering was uncommon in federal trials but not altogether unexpected in this case.

“In Minnesota, a scheme to pay jurors is rarer than a snowless December,” he said. “But this case is such an outlier in the size and sweep of the alleged fraud that I can’t say this is shocking news, if true.”

Mr. Lillehaug said the judge and lawyers in the case were deeply experienced, and he predicted the incident would not derail the trial.