Brazilian doctor Virginia Soares de Souza has been charged with killing seven patients in an intensive care unit to make room for others. She is now being investigated for up to 300 deaths that occurred at the Evangelical Hospital in Curitiba.

Prosecutors claim that with the help of her medical team, 56-year-old De Souza killed her patients by giving them muscle relaxants before cutting their oxygen supply, and thus, asphyxiating them.

The prosecutors claim that through a wiretap they were able to hear De Souza admit to the crimes, stating that she did so in order to free up hospital beds. She has been charged with seven counts of first degree murder, and seven other professionals on her team have received similar charges.

"I want to clear the intensive care unit. It's making me itch," De Souza said in one recording released to Brazilian media. "Unfortunately, our mission is to be go-betweens on the springboard to the next life," she added.

The Brazilian Health Ministry's investigator Maria Lobato is now re-examining the 1872 deaths that have taken place at the hospital over the past seven years while De Souza was in charge. Lobato has said that so far 20 of these deaths have now been deemed 'suspicious,' and 300 more are under review.

A lawyer for De Souza was quick to dismiss those numbers, stating that Lobato is "trying to sensationalize with the number of deaths in an intensive care unit." He continues: "Does that mean that nobody died from causes resulting from their own condition? That would be a unique case worldwide."

The investigation's documents indicate that De Souza was not always present for the killings, but instead would at times give authorization to her workers over the phone. She denies any wrongdoing in the deaths.

"I was never negligent, careless. I was never blamed for ethical violations and I practiced medicine in a conscientious and correct manner," De Souza told the Brazilian television station Globo on Sunday.

If Lobato and court prosecutors are able to prove that De Souza did kill 300 people in her care, it would represent one of the worst serial killings in history. Currently, the worst known incident of a doctor intentionally killing his patients is the case of Harold Shipman, an English doctor who was found to have murdered at least 215 individuals.