An Amtrak passenger made an unexpected discovery when he walked off a train at Washington, D.’C.s Union Station with the wrong backpack.

He found $17,900 in cash inside. And in doing so, he triggered a federal investigation that’s since been linked to a convicted drug dealer in New York.

The incident happened in 2014, but was just recently revealed by federal agents who are seeking to formally seize control of the money.

According to a report from investigators obtained by the News4 I-Team, the man mistook the backpack for his own as he left the train. Afterward, he discovered the cash tucked inside the bag. The man, who is referred to only by the initials M.M.A. in court records, notified Amtrak police.

According to paperwork filed by federal prosecutors in U.S. District Court for the District of Columbia, the money was linked to another passenger aboard the train, a man named Peter Rodriguez, who remained on board until the Amtrak train reached New York City.

The court filings said Rodriguez acknowledged being the owner of the bag, but denied carrying money in it. News4 was not able to reach Rodriguez for comment.

Court records said Rodriguez’s mother, Angela Rodriguez, later called investigators claiming the cash belong to her and her partner. She said the pair had recently sold mink coats to raise cash to buy a car during a visit with her son in North Carolina, the court filings said.

Rodriguez told agents she’d mistakenly left the cash behind inside a brown paper bag when she returned home to New York. She told agents she’d asked her son to bring the brown paper bag of cash with him in his backpack during his train trip north to New York, without specifying what was inside the bag, according to court records.

A federal prosecutor, in a filing with the federal court, said Angela Rodriguez and her partner did not “provide documents to substantiate central elements of their narrative, such as their travel to North Carolina.”

The agents also reported a police narcotics dog had “alerted” to the presence of the residue of narcotics when searching the backpack in a police office.

Peter Rodriguez was convicted in October 2014 in New York state court for selling drugs. The feds now are seeking to hold the money through the civil forfeiture process.

A Justice Department official told the News4 I-Team the money is secured and transported to a financial institution, where it is then counted and a check is issued by the financial institution to the United States Marshal’s Service.