(The Hill) — Hospitals and clinics in five states are facing disruptions due to a cyberattack Thursday that forced some emergency rooms to close.

The attack began at facilities operated by Prospect Medical Holdings. The company’s facilities in California, Texas, Connecticut, Rhode Island and Pennsylvania were affected by the cyberattack.

“Upon learning of this, we took our systems offline to protect them and launched an investigation with the help of third-party cybersecurity specialists,” the company said in a statement Friday.

“While our investigation continues, we are focused on addressing the pressing needs of our patients as we work diligently to return to normal operations as quickly as possible.”

Beyond impacting emergency rooms, the attacks caused the closures of some primary care services and ambulance diversions. 

The affected medical facilities were recovering from the attacks as of Friday, though the process could take weeks, said John Riggi, the American Hospital Association’s national advisory for cybersecurity and risk.

At the moment, some of the hospitals have reverted back to keeping paper records, or using humans to oversee certain services that computer systems would normally monitor.

“These are threat-to-life crimes, which risk not only the safety of the patients within the hospital, but also risk the safety of the entire community that depends on the availability of that emergency department to be there,” Riggi said.

The Associated Press contributed to this report.