A New Hampshire hospital has agreed to pay $300,000 to settle allegations that it violated federal law by failing to keep accurate records of controlled substances, including opioids, the U.S. Attorney's Office said.

The Drug Enforcement Administration launched an investigation at Catholic Medical Center in Manchester last year that found an anesthesiologist nurse had diverted liquid fentanyl left over from medical procedures instead of properly disposing of it and had falsified disposal records, the U.S. Attorney's Office said Monday. The investigation also found the nurse had stolen controlled substances about once a day for a year.

The nurse pleaded guilty last month to tampering with consumer products, admitting she substituted saline and another drug for liquid fentanyl intended for a surgical patient. She is awaiting sentencing.

A DEA review of the hospital's records showed that the hospital's inventory of seven controlled substances, including fentanyl, was not accurately reflected because the hospital possessed larger quantities of the drugs than indicated in its records, the U.S. Attorney's Office said.

The Catholic Medical Center has not admitted liability, the U.S. Attorney's Office said. The center is cooperating with the investigation and has taken important steps to improve its controls and procedures to prevent future theft and abuse of controlled substances, the Attorney General's Office said.

“Catholic Medical Center is committed to maintaining the highest standards and a rigorous drug abuse prevention program,” the hospital said in a statement. “Upon learning of this incident, CMC took immediate action, promptly notified federal and state authorities, and cooperated fully throughout the investigation.”