Police detained nearly 10 people in a raid on a hospital in Plovdiv and a building at Plovdiv Medical University, suspected of defrauding the national health fund through fake hospital admissions. Economic crime police are leading the investigation.

Those detained include Professor Mariela Geneva-Popova, dean of Plovdiv Medical University's medical faculty and head of its rheumatology clinic. All were taken in for questioning, and some were held under 24-hour police arrest.

Two sisters are among those held: Dr Tsvetalina Kolacheva Sali, a doctor at the rheumatology clinic, and Dr Fani Kolacheva Gudeva, who owns and runs three rehabilitation centres. Kolacheva-Sali was the only one later placed under arrest, but she has since been released under house arrest.

Investigators believe she organised fake hospital admissions under clinical pathways and oversaw the issuing of false sick-leave certificates. Patients were then sent for rehabilitation to one of her sister's three centres, and later for "continued treatment" at a sanatorium in the village of Banite, in the Smolyan region, where the family has relatives.

Kolacheva-Gudeva's three centres are Fizioterapia Yug in Plovdiv's Kyuchuk Parizh district, the Dinamikmed medical centre in Asenovgrad's Dolni Voden district, and a specialised physiotherapy and rehabilitation clinic in the town of Kuklen.

Police teams searched the rheumatology and nephrology clinics. Both stopped work while investigators finished their search, leaving patients waiting outside. Officers seized a large number of documents, and some of those detained were filmed being led away.

Patients said doctors' phones had been seized and no one would tell them why they could not go into the consulting rooms. Some had come for a panel review to get expensive biologic drugs prescribed, others for a check-up, and others for admission to hospital.

The search at the nephrology clinic was still under way. Unofficial sources say no medical staff from that unit have been detained so far.