On Friday, former Green Party candidate Jill Stein—who launched a recount effort in Michigan, Wisconsin and Pennsylvania following the election of Donald Trump—asked U.S. Attorney General Loretta Lynch to investigate the integrity of the nation’s electoral system, the Hill reports.

“We write to urge the Department of Justice to launch an investigation into the integrity of our nation’s election system generally, and our nation’s voting machines specifically, based on the information we discovered in the course of this representation,” Stein’s counsel wrote in a letter to Lynch.

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The letter urged the department to focus specifically on human and machine error that may impact voting machines in future elections.

“The attempted recount process has uncovered that voting machines relied on in these states and across the country are prone to human and machine error, especially in under-resourced black and brown communities, and vulnerable to tampering and hacking,” the letter read.

Stein argued states’ “insufficient efforts” to protect the systems in low-income communities and communities of color “warrants federal intervention.”

Stein spearheaded the effort to audit the vote in November, filing lawsuits in three swing states to verify the final tallies. A recount in Michigan reaffirmed Trump’s win, while similar efforts in Wisconsin and Pennsylvania were struck eventually down by the courts.

After he won the election Trump tweeted—without evidence—that he would have won the popular vote were it not for “the millions of people who voted illegally.” Despite stoking fears of voter fraud himself, Trump launched an aggressive campaign to discredit Stein’s recount, calling it “lawless” and “insulting.”

In the final popular vote count, Hillary Clinton beat Trump by 2.9 million.