Federal prosecutors have charged delivery service FedEx with working with two online pharmacy companies to deliver prescription drugs without a prescription.

The FDA announced on Thursday that the charges were filed by the U.S. Attorney for the Northern District of California. Prosecutors allege that FedEx is violating the Federal Food, Drug, and Cosmetic Act, which requires customers to present a valid prescription from a doctor in order to receive prescription medication. However, these two online pharmacy companies were allegedly not requiring them and FedEx was delivering the medication.

Agents from the U.S. Drug Enforcement Administration and the FDA’s Office of Criminal Investigations led the investigation. The agencies have worked with prosecutors to curb illegal prescription drug distribution.

In a statement, FedEx said that it vows to fight the charges and will plead not guilty. The company claims that it has worked closely with the government in the past to stop illegal prescription drug distribution.

“We have repeatedly requested that the government provide us a list of online pharmacies engaging in illegal activity,” the company stated. “Whenever DEA provides us a list of pharmacies engaging in illegal activity, we will turn off shipping for those companies immediately. So far the government has declined to provide such a list.”

However, Time reports that prosecutors claim that FedEx has been warned in the past and ignored these warnings.