You cannot have a situation whereby a nurse has the power of life and death

Hungarian Health Minister Istvan Mikola

The woman, identified only as Timea F, has been dubbed the Black Angel.

Hungary's health minister ordered the nationwide inquiry after claims that the nurse was free to kill because of gaps in procedures.

"I have ordered an investigation by the Public Health Officer at every Hungarian hospital to regain the confidence of the public in the health service," said the minister, Istvan Mikola.

"Whatever a hospital's procedures may be, you cannot have a situation whereby a nurse has the power of life and death."

Takacs: System cannot protect against a psychopath

The nurse, who apparently carried out the killings during night shifts, is undergoing psychiatric evaluation. The deaths are believed to be spread over the past year.

The Gyula Nyiroe hospital where the killings took place has said it is not to blame for the killings.

"In the current situation, I do not feel that even a limited responsibility of doctors could be established," said hospital director Gabor Takacs.

"If a psychopath, or a person with mental disorders or personality deviations - one who thinks to be master of life and death - gets into the system, the system cannot protect itself," he added.

If you ask whether she had made any serious mistake that could have alerted us, the answer is no

Department head Mariann Vadnai

The nurse worked in a special unit for the terminally ill, and has reportedly told police she wanted to spare the patients any further suffering.

Managers insist they had been given no cause for concern about her conduct.

"She had worked here for six years and was an experienced, professionally well-trained nurse. If you ask whether she had made any serious mistake that could have alerted us, the answer is no," department chief Mariann Vadnai told a press conference.

The alarm was raised when a colleague finally saw the nurse giving dying patients intravenous injections without a doctor's prescription.

Police spokesman Attila Petoefi said the case was "unprecedented" in Hungarian police and medical history.