MINNEAPOLIS (AP) — A federal judge on Wednesday ordered defendants in all upcoming cases stemming from a major COVID-19 pandemic fraud case in Minnesota to stay away from her courtroom after allegations of witness tampering surfaced in the trial of the alleged ringleader. Prosecutors say the scheme stole $250 million from a program meant to feed children.

Aimee Bock, who founded and led the now-defunct nonprofit, went on trial this month with Salim Said, a former co-owner of Safari Restaurant in Minneapolis, for their alleged roles in the scheme. They’re among 70 defendants charged in the investigation. Many of them have already pleaded guilty. The others are being tried in batches.

U.S. District Judge Nancy Brasel imposed the restrictions a day after Assistant U.S. Attorney Joe Thompson made the allegation. He said in court after testimony ended Tuesday that the alleged attempt was especially troubling in light of an attempt in June to bribe a juror in the first trial of defendants in the sprawling fraud case, which centers on a group called Feeding Our Future.

Prosecutors have called it one of the country’s largest pandemic-related fraud cases. The first trial was marred by an alleged attempt by some defendants and people linked with them to bribe a juror with a bag of $120,000 in cash. The juror went straight to police.

“Here we find ourselves again with people trying to corrupt our process,” Thompson told the judge.