A hospital in Los Angeles has been operating without access to email or electronic health records for more than a week, after hackers took over its computer systems and demanded millions of dollars in ransom to return it.

The hackers that broke into the Hollywood Presbyterian Medical Center’s servers are asking for $3.6 million in Bitcoin, a local Fox News affiliate reported. Hospital staff are working with investigators from the Los Angeles Police Department and the FBI to find the intruders’ identities.

Meanwhile, without access to the hospital’s computer systems, doctors and nurses are communicating by fax or in person, according to an NBC affiliate. Medical records that show patients’ treatment history are inaccessible, and the results of X-rays, CT scans, and other medical tests can’t easily be shared. New records and patient-registration information are being recorded on paper, and some patients have been transferred to other hospitals.

A recording on a media-relations phone line at the hospital said that “patient care has not been compromised” after the cyberattack, but a spokesperson was unavailable for further comment.

The fact that hackers were able to encrypt patient records doesn’t necessarily mean they gained access to those files, but the goal of this type of cyberattack isn’t to get to patient information; it’s to make sure that the hospital can’t get to it, either. Viruses and malware that take over a server or a computer and demand money to return it are known as ransomware. The tactic has spread in popularity in recent years, as hackers take advantage of the increase in networked devices, gadgets, and servers.