Even as some staff reported improvements, MedStar Health continued to suffer computer problems Thursday after a crippling hack locked up data on its systems earlier in the week.

“MedStar continues to move toward full restoration of major IT systems, while maintaining its promise to meet the care needs of the communities we serve,” the health system said in a statement issued late Thursday afternoon.

One doctor who works at a MedStar hospital in Baltimore said things appeared to be getting better and that the computer systems he uses are back online.

“At least from my use, things are back to working,” the doctor said. He asked not to be named because MedStar has not authorized employees to talk to reporters.

But another doctor, who also asked not to be named for the same reason, said he had noticed little improvement since Wednesday.

“Things are making small progress here and there,” he said.

MedStar first noticed problems Monday morning and pulled its systems offline to stop what it has described as a computer virus from spreading. The virus appears to be a type of “ransomware,” which encrypts files, making them inaccessible to the original users.

Hackers have demanded an $18,500 payment for the keys to decrypt the data.

The health system has not officially acknowledged that it was the victim of a ransomware attack. MedStar says there's no evidence that patient or employee data has been compromised, but it's not clear whether it has been able to retrieve or replace any data that was encrypted.

Clinical staff have described a slowdown in work as they switched to backup paper systems, but MedStar said the numbers of people treated at its 10 hospitals and other facilities across the region have been close to normal.

The health system said that in a few cases there have been disruptions to treatment.

Baltimore Sun reporter Andrea K. McDaniels contributed to this article.

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