Federal agents may have violated state laws while accessing voter records as part of the Trump administration’s effort to identify noncitizens on state voter rolls, The New York Times reported Monday.

The investigation, known as the “Unlawful Voter Initiative,” has reportedly deployed hundreds of federal agents to examine voter-registration databases for evidence that noncitizens are voting in large numbers. The operation was first exposed in a New York Times report published last month, which said a whistleblower alleged that federal agents had been ordered to conduct a broad search for voter fraud.

The latest New York Times report said the effort may depend on questionable data, rushed reviews and investigative practices that could conflict with state law. The whistleblower said agents were required to complete at least 40 reviews in eight hours, leaving limited time to examine each voter’s citizenship and voting history.

“This is just the latest example of how far Donald Trump will go to interfere in our elections,” Sen. Chuck Schumer (R-N.Y.) said in an interview.

“We’ve never seen anything quite like this. They come up with so many different ways to try and steal the election, to try and jaundice the election, but we’ve never seen anything quite like this. Department of Homeland Security is actually pulling away these law officers, these federal law enforcement officers, away from the work they’re supposed to do,” he added.

Democratic senators sent a letter to Homeland Security Secretary Markwayne Mullin demanding that the operation be halted while they seek answers.

Former Homeland Security chief of staff Miles Taylor also raised concerns Monday in a column. He said the software used to control a national voter database gives any hacker the ability to flip a switch and nullify voters’ eligibility to cast a ballot and have it counted.

The whistleblower said federal agents were reviewing personally identifiable information from internal government records and external sources, including birth dates and partial Social Security numbers. The whistleblower questioned whether using that information to search voter records was legal.

“The agents plugged those names and personal data into public-facing state websites to find a subject’s voter history,” the report said. “Some states, such as Virginia, declare explicitly that only individual voters may use the search tool to look up their own records. Others, such as California, require specific information such as a driver’s license number or partial Social Security number in an effort to limit the use of the tool to individuals.”

The whistleblower said the practice was flagged to officials leading the investigation within Homeland Security’s Fraud Detection and National Security Directorate. The whistleblower was told that agents could use the database for work related to the voter-search initiative. “Yet leadership appeared to acknowledge the potential for legal liability...” the report said.

Leadership told the whistleblower that agents “are not personally liable for conducting these searches when done as part of their official duties and properly documented.”

“This statement suggests that there may be legal implications for accessing these websites,” said a report by the government watchdog group Democracy Defenders Fund, which has worked with the whistleblower and provided legal representation. “Yet they are still requiring officers to engage in this illegal activity with promises of personal liability protection.”