A major cyberattack is delaying response times on the UK’s NHS 111 telephone service which is used for medical emergencies, the Telegraph has reported.

The target of the breach was Advanced, which is owned by private equity firms. It provides software for about 85% of the hotline’s services, according to the newspaper. The hackers were part of an organized criminal network, according to an updated version of the report.

The company’s Adastra system allows call handlers to dispatch ambulances, book urgent appointments or fill emergency prescriptions.

Cases requiring an ambulance are given priority, according to the newspaper citing a National Health Service source. Systems could remain offline until August 9.

Simon Short, chief operating officer of Advanced, said a security issue was identified on August 4 and as a precaution, the health and care systems were immediately isolated. The company’s services also extend to nursing homes and a patient records management system.

Advanced is owned by Vista Equity Partners and BC Partners.