The top transportation directors in Maryland’s largest school district are now on leave pending a criminal investigation by local police.

Todd Watkins, director of the transportation department at Montgomery County Public Schools (MCPS), and assistant director Charles Ewald were placed on leave after the district reported “allegations of possible financial improprieties,” according to an official statement released by the school system.

“We take these allegations very seriously, and as a result, we immediately contacted the police to investigate,” the statement said. “We are not able to share additional details while the investigation is proceeding.”

In the interim, Watkins and Ewald have been replaced by Michael Lewis and Kathy Herald.

“MCPS is committed to fully supporting and understanding all aspects of this investigation; based on what we learn, we will determine next steps,” the district statement said. “Students are our first priority, so it is important to note that the safe transportation to and from school each day will not be impacted.”

In recent years, Watkins has developed a national profile as an advocate for fleet electrification. Earlier this year, MCPS partnered with a Highland Electric subsidiary to replace 326 diesel school buses with Thomas Built Saf-T-Liner C2 Jouley buses. He was also interviewed on PBS NewsHour about seat belts on buses.