All sections of the All India Institute of Medical Sciences (AIIMS) in Delhi have been functioning manually since 7 am on Wednesday after the hospital reported a server failure.
Officials have been manually managing the Out Patient Department and sample collection services, though the sample system for those who do not have a Unique Health Identification (UHI) number has been affected.
As each sample collected requires a barcode for tracking, the server going down has led to very few samples being collected, an AIIMS official told PTI.
In a statement issued in the evening, the hospital said that the National Infomatics Centre, which is working to restore the system, has informed that this may be a ransomware attack.
"Measures are being taken to restore the digital services and support is being sought from Indian Computer Emergency Response Team (CERT-In) and National Infomatics Centre," the statement read.
"AIIMS and NIC will take due precaution to prevent future such attacks. As of 7.30 pm, the hospital services are running on manual mode," it further said.