There have been several high-profile and particularly brutal crimes on New York’s subway in recent years, including a woman getting set on fire, the killing of a homeless man, and a series of incidents in which people have been pushed in front of trains.

In a letter to MTA Chair Janno Lieber, U.S. Transportation Secretary Sean Duffy demanded a list of “actions and plans to reduce crime on its system,” including rates of assaults, fare evasion and train surfing in the subway.

The Trump administration is threatening to withhold federal funding from the agency that runs the New York City subway if the Metropolitan Transportation Authority doesn’t comply with a request for information on transit crime.