Iva Mihaylova will stay at Pirogov emergency hospital until early next week, the hospital told Bulgarian National Radio.
This story follows our earlier report on Mihaylova's secret return from North Macedonia and her treatment at Pirogov.
She faces more specialist tests to establish her condition, and doctors will then decide how to continue her treatment. She has been in the hospital since Monday, when she returned to Bulgaria with her lawyer.
North Macedonia's interior ministry is searching for her at home and abroad on an order from the court in Kocani. The court says Mihaylova broke a ban on leaving the town and the country.
A day earlier, prime minister Hristijan Mickoski said in a TV interview that North Macedonia had talked to its international partners. He said a NATO member had become a safe haven for convicted criminals, so he will raise the case at NATO and EU meetings.
Mickoski expects Mihaylova and her father to be brought to justice as soon as possible. The father lives in Bulgaria and has a sentence in North Macedonia.