Employees from P & W Railroad alerted police after they saw four individuals dropping loads off a bridge on Route 122.
As a result, the Uxbridge Police Department is asking residents to stop pooping on trains.
"I don't have any words for it. It's disgusting," Police Chief Jeffrey Lourie told the Telegram & Gazette. "It's a violation of the law. Their actions pose no lawful purpose."
This isn't the first time that someone has gone number two on top of this particular train.
"It's disgusting. It's not just gross, but it creates a health and safety issue for our employees," said P & W general counsel Charles Rennick. "It's hard to wrap your mind around the fact that someone would do that."
If the suspects are caught, they could be charged with disorderly conduct, disturbing the peace, and open and gross lewdness.
"Yes you read that right, we have no idea what would possess someone to drop their pants and poop on a passing train, but guess what it is happening," the UPD wrote on its Facebook page.
"Take this as a warning... If we catch you with your pants down defecating on the train you will be charged with everything we can find that fits the elements to the crime."