Boar’s Head processing plants nationwide are now part of an ongoing law enforcement investigation, the U.S. Department of Agriculture disclosed Thursday, in the wake of a deadly outbreak blamed on some of the company’s now-recalled deli meats. 

At least 59 hospitalizations and 10 deaths have been linked to a listeria strain traced back to Boar’s Head products distributed from a now-shuttered plant the company ran in Virginia. 

That Boar’s Head plant in Virginia had been written up dozens of times by inspectors over violations, CBS News first reported in August, based on records obtained through a Freedom of Information Act request. Violations flagged at the plant by agriculture officials included mold and insects found throughout the site. 

The USDA disclosed the existence of the probe in a letter on Thursday, when it denied a CBS News request for records on Boar’s Head’s other plants in Michigan, Arkansas and Indiana.

Since the records are being “compiled for law enforcement purposes,” the department said releasing them “could hinder the government’s ability to further control and shape the investigation.”

“Given the ongoing investigation related to this matter, FSIS is withholding 93 pages in full,” they wrote. 

The disclosure comes the same day as a letter by Sen. Richard Blumenthal and Rep. Rosa DeLauro, both Connecticut Democrats, to the USDA and the Department of Justice, urging them to consider criminal charges against the company.

“The time for action is long overdue, and we urge your agencies to work together to seek immediate justice for impacted consumers and to prevent this from happening again,” they wrote.

It is unclear whether the probe is a criminal or civil investigation. An FSIS spokesperson did not immediately respond to a request for comment.

A Boar’s Head spokesperson declined to comment, saying the company does not comment on legal matters.