Federal authorities are investigating the police department in Irving, Texas, in connection with the September arrest of a high school student whose homemade clock was mistaken for a bomb, U.S. Attorney General Loretta Lynch said Thursday.

"We have, as you may know, opened an investigation into the case of the young man in Irving," Lynch told a crowd in suburban Washington, D.C. "So we will see where that investigation goes."

Irving MacArthur High School freshman Ahmed Mohamed was arrested but not charged in September after he brought a homeclock to school. The 14-year-old told NBC DFW he hoped it would impress his teachers.

School officials and authorities grew suspicious of the clock — assembled and placed in a small briefcase — and suspected it was a bomb, or a hoax of some sort.

Lynch announced the federal investigation while speaking at a dinner Thursday held by the Muslim Advocates, a national legal advocacy group for the rights of Muslims, according to the Los Angeles Times.

"At this time, the City of Irving has received no communication from the U. S. Department of Justice regarding an investigation into the Ahmed Mohamed case," Public Information Officer James McLellan told NBC when reached via email.

Mohammed's family threatened a lawsuit against the Irving Independent School District and demanded $15 million and an apology. The family has since moved to Qatar.

NBC 5's Todd L. Davis contributed to this report.