The authorities say they suspect Miss Wagner, who worked in the first ward since 1982, of responsibility for most of the killings. Among the drugs used were insulin and tranquilizers.

According to the detention warrant, she showed the others how to make up the lethal injections or let them watch as she held a patient's tongue and nose and poured water into their lungs. Alois Stacher, the head of Vienna's health department, said the warrant quoted Mrs. Leidolf as saying she was ''convinced that 100 patients were killed in each of the last two years by Wagner.'' Part of Confession Withdrawn

But Miss Wagner has withdrawn parts of her confession since she was apprehended on April 7. Press reports say she is now admitting to having killed only nine people. Wilhelm Philip, her attorney, refers to a ''so-called confession,'' and says it would not be enough to convict her of murder.

The warrant quotes her as saying she killed an average of three people a month since last summer and as identifying 26 victims.

While the grisly details are slowly being unraveled by the legal authorities, the fallout in the health system has been rapid. The first ward and another ward in Pavilion V have been closed because of staff shortages. Dr. Franz Xavier Pesendorfer, the head of the ward, was suspended on April 12 by Mr. Zilk, reportedly because he failed to pursue rumors of mass killings in his department that surfaced a year ago. Doctor Defends Actions

At a news conference today, Dr. Pesendorfer defended his actions, saying he had alerted the authorities, doctors and supervisory nurses and ordered autopsies as soon as suspicions were raised. ''What more could I have done?'' he said.

Dr. Pesendorfer said the dead were not victims of the system but victims of crimes that could not have been anticipated and prevented.