CHICAGO (AP) — Two dozen people are facing federal drug charges after prosecutors say they used Amtrak trains to transport cocaine and heroin from California to Chicago.

The U.S. Attorney’s Office in Chicago says the charges are part of a multi-year investigation dubbed “Operation Derailed.”

In a news release, prosecutors say the defendants received large amounts of heroin and cocaine from traffickers in Mexico and California. They moved it from Los Angeles to Chicago aboard the Amtrak Express, a commercial train line. Some drugs were concealed inside pool filters and car parts.

One of the people named in the indictment unsealed Thursday is an Amtrak employee who’s accused of stealing a package of cocaine after it arrived at Union Station in Chicago.

(TM and © Copyright 2016 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)