Given the tech giant’s “size and scope,” Rubio and Brown write that the company should receive “particular scrutiny by federal regulators” as it faces a number of “widespread and credible” allegations of labor and employment law violations.

In their letter, the two senators draw on reports that the company has subjected employees to “grueling hours” and exhibited a “general lack of responsiveness” to the concerns voiced by employees over the company’s “highly automated management practices.”

More specifically, the letter references an allegation from the girlfriend of a former warehouse employee at a facility in Edwardsville, Illinois, who said that her boyfriend had sent a message stating that the company would not allow him to leave work despite the area facing a major storm. A tornado brought on by this storm ultimately struck the facility, resulting in the death of this employee and five others.

In addition to this allegation, a number of outlets have reported employees not having time to use the restroom and being forced to urinate in bottles as a way to keep up with quotas. The letter also references a report from The New York Times that “widespread human resources mismanagement” had resulted in the wrongful termination of employees.