Delhi Police have registered a case against unknown persons in the ransomware attack against servers of AIIMS-Delhi which have been down for more than 24 hours, officials said on Thursday.

After they came to know about the attack, the hospital authorities approached the south district police which then transferred the matter to the Intelligence Fusion and Strategic Operations (IFSO) unit of Delhi Police.

Servers for National Informatics Centre's eHospital used at AIIMS-New Delhi have been down since 7 am Wednesday, affecting the healthcare centre's outpatient department (OPD) and sample collection services.

Since the servers went kaput, all these services have been running on manual mode, AIIMS authorities had earlier said.

A team from the National Informatics Centre (NIC) working at AIIMS has speculated the attack may have been caused by ransomware.

The attack has been reported to the appropriate law enforcement authorities, AIIMS had said in a statement.

"With the server being down, the outpatient and inpatient digital hospital services, including smart lab, billing, report generation and appointment system, among others have been affected," an AIIMS official had said.

The OPD and sample collection were handled manually but the sample collection system for those who do not have a Unique Health Identification remain affected, another official had said.

As each sample collected requires a barcode for tracking, the server going down has led to very few samples being collected, he said.