An internal review of All Children’s Hospital in St. Petersburg, Florida, has found more than a dozen incidents in which children in the hospital’s heart unit were harmed by the care they received, the Tampa Bay Times reports. All Children’s is owned by a branch of Johns Hopkins Medicine, and in 2011, the hospital’s board gave over near-complete authority to Johns Hopkins, which is based out of Baltimore, Maryland. “Leadership knew there were quality and safety issues and did not elevate it in appropriate ways to the board,” said Kevin Sowers, president of the Johns Hopkins Health System. “(Johns Hopkins) let this organization down.” A November investigation by the Tampa Bay Times revealed that the heart unit’s mortality rate had tripled in just two years to become the highest in Florida. Employees began bringing concerns about two of the unit’s surgeons to their supervisors in late 2015, but hospital administrators did not slow surgeries or make personnel changes until 2017, according to the investigation.

Since that report, the hospital’s CEO, two heart surgeons, and three vice presidents in charge of risk management, patient safety, and communications all resigned. The federal government gave the hospital until Sunday to propose a plan for how it will address the issues.