Police in New Jersey arrested a teacher this week for allegedly sexually assaulting a 3-year-old student, prosecutors say. 

A coworker observed Thomas Meier, 35, of Mount Arlington, "engaged in an act of sexual contact" with the child on Oct. 8, Morris County prosecutors say. 

Meier was a teacher at Head Start of Morris County at the time of the alleged incident, according to prosecutors. 

Prosecutors have charged Meier with one count of second-degree sexual assault and one count of second-degree endangering the welfare of a child. 

He is being held at the Morris County Correctional Facility pending a court appearance, the prosecutor's office said.

Attorney information for Meier was not immediately available Saturday.