There was initial confusion about the number of victims, with local authorities reporting nine dead among the 10 patients in the unit treating serious COVID-19 cases.
However, prosecutors investigating the fire later said only seven people had been killed, Interior Minister Lucian Bode told a news conference.
Firefighters extinguished the fire after an hour, with help from additional teams brought in from nearby regions.
Patients and staff at the facility were evacuated, authorities said. Bode said that 125 patients were in the hospital at the time of the fire.
Romania is reeling under a new wave of COVID-19 infections, even as the vaccination rate for its population is second-lowest in the European Union.
The government has struggled to boost the number of intensive care beds and direct more resources for treatments and medication. As of October 1, there were only six inensive care unit beds available in the whole country, health officials said.
President Klaus Iohannis said in a statement that he was "horrified" by the incident. "The Romanian state failed its basic mission of protecting its citizens," he said.