SAN DIEGO (AP) — Scripps Health is trying to thwart a ransomware attack that has crippled its computers for three days and caused confusion for patients of the San Diego hospital system.

The Union-Tribune says the cyberattack that hit Saturday has put patient records, scheduling and other critical systems offline.

Medical personnel are reverting to paper for the time being.

Scripps has not publicly confirmed that the outage was caused by ransomware — malicious software that locks up computer data and demands ransom payments in order to give it back. But the Union-Tribune obtained an internal Scripps memo that implicates a cyberattack.