The federal investigation into Jane Sanders, the wife Sen. Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE (I-Vt.), has reportedly escalated in recent months, The Washington Post reported on Monday.

Prosecutors have taken more than a dozen boxes containing documents and records from Burlington College, where Jane Sanders once served as the school’s president, the Post reported, according to interviews and documents.

A state official has also reportedly been called to testify on the matter before a grand jury.

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The newspaper reported that half a dozen people said federal prosecutors or investigators had contacted them recently.

Jane Sanders’ lawyers also interviewed these individuals to determine what they might tell investigators, former college trustees told the Post.

The FBI is reportedly looking into whether Jane Sanders falsified loan documents while serving at the school, which closed down in May 2016 after going bankrupt and failing to meet accreditation standards.

A Vermont-based blog, VTDigger, reported last year that Jane Sanders inflated how much the small Vermont college had secured in donations, noting two instances in which a person said the amount of their financial pledge had been exaggerated on the school's loan application.

Brady Toensing, a Vermont Republican lawyer who chaired President Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE’s campaign in the state, requested the Justice Department open a fraud investigation after learning about the VTDigger report.

The Sanderses have hired two top D.C.-based lawyers to represent them during the ongoing probe, which reportedly started in January.

The FBI has not filed formal charges against Jane Sanders at this time.

Bernie Sanders, the former 2016 Democratic presidential contender, blamed partisan politics for fueling the probe against his wife.

"Right in the middle of my presidential campaign, I know this will shock the viewers, the vice chairman of the Vermont Republican Party, who happened to be Donald Trump's campaign manager, raised this issue and initiated this investigation," he told CNN’s Jake Tapper earlier this month.