Following a BuzzFeed News investigation, a leading Republican senator has called for a federal probe into a troubled youth psych facility and its parent company, Universal Health Services, America’s largest provider of psychiatric care.

Describing “a pattern of conduct that is extremely concerning and casts a dark cloud over UHS’s ability to properly care for its patients,” Charles Grassley, the chairman of the Senate Judiciary Committee, gave the Department of Health and Human Services a deadline to report back to him on “what steps your office is taking to investigate UHS for the aforementioned abuses.”

In addition, Grassley called on The Joint Commission, an organization that accredits hospitals, to explain how it came to award a “Gold Seal of Approval” to Shadow Mountain Behavioral Health, in Tulsa, OK.

BuzzFeed News’s investigation revealed a deeply troubled facility, with a ward that has boiled over into a riot, nurses who battle drug addiction, doctors who feel pressured to admit patients, and a bare-bones staff unable to control the violence. Surveillance videos also showed the director of the hospital putting several of the hospital’s young patients into holds that one expert called “dangerous” and “totally unnecessary.”

UHS has praised the quality of care at Shadow Mountain,and said that the videos were taken out of context and could not be understood without access to the patients’ treatment history.

Oklahoma has repeatedly put Shadow Mountain on probation for charges including failing to maintain an adequate staff, improperly dispensing medication, and failing to report sexual misconduct. UHS challenged these findings.

In response to questions from BuzzFeed News, Oklahoma’s Department of Human Services, which investigates child abuse and neglect, recently opened an investigation into Shadow Mountain and its director, Mike Kistler. Oklahoma’s Republican governor and senior senator have also called for a thorough investigation into the facility.

This is the second occasion on which Sen. Grassley, who represents Iowa, has written to the office of the inspector general of the Department of Health and Human Services about UHS. The last was in December, after BuzzFeed News revealed that employees at ten UHS facilities across nine states said they were under pressure to fill beds by almost any means, including twisting people’s words to make them seem suicidal.

The Iowa senator set an April 28 deadline for responses from both the Office of the Inspector General and the Joint Commission.