Hospitals and clinics in Texas, Connecticut, Rhode Island and Pennsylvania have been reportedly disrupted due to a cyberattack.

According to ABC News, the cyberattack has reportedly targeted computer systems of hospitals and clinics in several states. This has even forced some emergency rooms to close and ambulances to be diverted. On Friday, many primary care services remained shut as security experts worked to determine the root of the attack and its extent in order to solve the same.

It started as a “data security incident” on Thursday at facilities operated by Prospect Medical Holdings. It is California-based company which runs hospitals and clinics in Texas, Connecticut, Rhode Island and Pennsylvania.

“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.”

The emergency departments at Manchester Memorial and Rockville General hospital in Connecticut were also were closed for a majority of Thursday. Patients were re-directed to other nearby medical centers.

“We have a national Prospect team working and evaluating the impact of the attack on all of the organizations,” Jillian Menzel, chief operating officer for the Eastern Connecticut Health Network, said in a statement.

The state’s FBI branch issued a statement saying it is working with “law enforcement partners and the victim entities.” It refrained from commenting further since it was an ongoing investigation.