A critical-care doctor in Ohio who authorities believe “purposely caused the death” of 25 hospital patients that overdosed on the opioid painkiller fentanyl was arrested and charged with murder Wednesday.

Dr. William Husel, 43, pleaded not guilty to 25 counts of murder charged against him by the Franklin County Grand Jury. A lawyer for Husel has said he did not intend to kill anyone.

The charges make up one of the biggest murder cases brought against a doctor in the United States. A judge posted bail at $1 million and Husel surrendered his passport at the request of prosecutor Ron O’Brien.

DISGRACED FRENCH DOCTOR ACCUSED OF POISONING 24 PATIENTS AS YOUNG AS FOUR TO SHOW OFF HIS TALENTS IN MEDICINE

O'Brien's office said in a statement that Husel ordered that patients receive doses of fentanyl "in various amounts between 500 and 2000 micrograms ... that shortened their life and hastened or caused their death."

The suspicious deaths occurred at Mount Carmel and St. Ann’s Hospitals in Columbus between Feb. 11, 2015, and Nov. 20, 2018, according to the statement.

Husel was fired from the Columbus-area Mount Carmel Health System in December 2018 and stripped of his medical license when allegations against him began to surface and an internal investigation by the hospital uncovered his fatal prescriptions.

More than two dozen wrongful-death lawsuits have been filed against Husel and the hospital system, some of which have been settled by the hospital for hundreds of thousands of dollars, according to the Associated Press.

Mount Carmel has admitted that Husel wasn't removed from patient care until four weeks after concerns about him were raised last fall and that three patients died during that gap after receiving excessive doses he ordered.

As a precautionary measure, all employees who worked with Husel to administer medication to the patients who died were removed from patient care. Forty-eight nurses and pharmacists were reported to their respective professional boards, 30 of whom were put on leave, and 18 no longer work at Mount Carmel, including some who left years before allegations surfaced.

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The prosecutor's office has said it does not intend to charge any other hospital employees and has not disclosed any possible motive.

The Associated Press contributed to this report.