The U.S. Department of Justice filed a lawsuit on Friday alleging Walgreens knowingly filled millions of unlawful prescriptions for controlled substances.

The pharmacy chain since August 2012 filled prescriptions that lacked a legitimate medical purpose, were invalid or weren’t issued in professional practice, the Justice Department said.

Walgreens is also accused of ignoring evidence, including from its own pharmacists and internal data, that stores were dispensing unlawful prescriptions.