A data breach at Prospect Medical Holdings triggers widespread disruptions, with emergency rooms closing and ambulances redirected across multiple states.

A cyberattack has severely disrupted hospital computer systems across the United States, leading to the closure of several emergency rooms and the diversion of ambulances on Thursday. The attack, identified as a “data security incident,” originated at facilities operated by Prospect Medical Holdings, a healthcare provider with hospitals and clinics in California, Texas, Connecticut, Rhode Island, and Pennsylvania.

In response to the breach, the company took its systems offline to contain the threat, while launching an investigation with the assistance of third-party cybersecurity experts. Many primary care services remained closed as security teams worked to understand the full scope of the damage and restore normal operations.

“Upon learning of this, we took our systems offline to protect them and launched an investigation,” the company stated. “While the 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 cyberattack has raised concerns about the vulnerability of healthcare systems, which handle sensitive data and are critical to public health. Experts are continuing to assess the impact, particularly on patient care, as hospitals scramble to mitigate the disruption.