A number of hospitals in London were forced to cancel operations and divert emergency patients following a ransomware attack on a critical supplier.

The incident has impacted Guy’s and St Thomas’, King’s College Hospital NHS Foundation Trusts, and primary care services across South East London, according to NHS England.

The disruption was a result of a ransomware attack on Synnovis, a third-party provider of essential pathology services, including blood tests, swabs, and bowel tests for the affected hospitals. Synnovis, in partnership with SYNLAB, is one of the largest pathology service providers in the UK, serving numerous NHS Foundation Trust facilities.

Synnovis CEO Mark Dollar confirmed that the attack had “affected all Synnovis IT systems, resulting in interruptions to many of our pathology services.” Due to these interruptions, the delivery of timely test results and diagnostic services has been delayed, leading to the cancellation of numerous surgical operations, including all transplant surgeries, because of the unavailability of necessary blood transfusions.

“This has resulted in a major impact on the delivery of services, such as blood transfusions and test results,” Dollar said.

In response to the crisis, Guy’s and St Thomas’ and King’s College Hospital declared a critical incident. Staff at these hospitals have been instructed to prioritize urgent and emergency test results, local media reported.

The list of impacted hospitals includes King's College Hospital, Guy's Hospital, St Thomas' Hospital, Royal Brompton Hospital, and Evelina London Children's Hospital. Due to the inability to perform healthcare procedures safely, some surgeries and other medical procedures have been canceled or redirected to other providers.

It’s currently unclear, what ransomware operation is responsible for the hack.