Alarmed by the “disturbing” practices of a major chicken processor in his state, U.S. Sen. Sherrod Brown of Ohio is demanding answers from the company, whose treatment of workers was detailed in a recent ProPublica and New Yorker investigation.

The story, published in May, documented how Case Farms, which supplies Kentucky Fried Chicken, Taco Bell and Boar’s Head, has for decades relied on immigrant workers to staff its plants, which are some of the most dangerous workplaces in America.

When these workers fought for higher pay and better conditions, Case Farms used their immigration status to get rid of vocal leaders, quash dissent and avoid paying for injuries. The story detailed how current immigration law makes it difficult for authorities to go after employers for hiring unauthorized immigrants, but easy for employers to retaliate against those workers.

In a letter sent to Case Farms CEO Tom Shelton on Wednesday, Brown said the investigation “raises serious questions about the company’s commitment to workers’ safety and workers’ rights.” Two of the company’s plants are located in Ohio. The Democratic senator asked Shelton what steps the company has taken to improve workplace safety and to detail if, and how, it has changed its policies regarding unionizing activities.

“Each infraction on its own is concerning,” Brown wrote, “but taken together they underscore a corporate culture at Case Farms that appears to emphasize profit maximization at all costs, including workers’ livelihoods and limbs.”

In an email, Mike Popowycz, the vice chairman of Case Farms, said the company would respond directly to Brown. In interviews for the original story and in a statement after its publication, the company said it treated employees well and was fixing the hazards cited by federal inspectors after several workers were severely injured at its plants.

This is the second time the ProPublica and New Yorker article has prompted action by public officials.

In May, the Ohio House of Representatives passed a bill that would have barred unauthorized immigrants from receiving workers’ compensation benefits if they were injured on the job. Opponents of the measure frequently cited the story to highlight what could happen to immigrant workers in the state if the bill were passed. In June, the state Senate stripped that provision from the bill.