Federal authorities have charged FedEx Corp. with assisting illegal pharmacies by knowingly delivering dangerous drugs to customers without prescriptions.

The Department of Justice announced the charges Thursday. The charges allege the Memphis, Tennessee, shipping company conspired with two related online pharmacies for 10 years ending in 2010.

FedEx is accused of shipping the powerful sleeping aid Ambien, anti-anxiety drugs Valium and Xanax, and other drugs to customers with no legitimate medical need and lacking valid prescriptions.

FedEx officials didn’t immediately return a phone call seeking comment.

FedEx first disclosed the federal investigation in a regulatory filing in November 2012. The company said at that time it had done nothing wrong and intended to fight any charges.