IRVING, Texas (AP) – U.S. Attorney General Loretta Lynch says the Department of Justice is investigating the brief arrest of a Muslim teenager who brought a homemade clock to his suburban Dallas high school.

Lynch confirmed Thursday that the department was investigating Ahmed Mohamed’s arrest.

Mohamed was detained, but quickly released, after police became suspicious of a clock he brought to school. His family questioned whether he was mistreated due to his religion.

The Dallas Morning News reports  that the Irving school district has refused to release an inquiry sent by the Justice Department.

Mohamed’s family eventually left Irving after reporting threats and now lives in Qatar. His lawyers have threatened the city and the school district with a lawsuit.