Ascension, a major U.S. healthcare network, is diverting ambulances from several hospitals due to a suspected ransomware attack that has been causing clinical operation disruptions and system outages since Wednesday.

Systems currently offline in impacted hospitals include the MyChart electronic health records system, which patients use to view their medical records and communicate with their providers. The attack also took down some phone systems and systems for ordering tests, procedures, and medications.

When it disclosed the incident on Wednesday, the healthcare giant was also forced to take some devices offline to contain what it described as a "cyber security event."

On Wednesday, the healthcare organization also advised business partners to disconnect from its systems immediately until further notice.

Because of ongoing operation disruptions and outages caused by the cyberattack and "out of an abundance of caution," Ascension also temporarily paused some non-emergent elective procedures, tests, and appointments while working to bring its systems back online.