IRVING, Texas (AP) — A suburban Dallas school district is suing the state of Texas to prevent the release of details of a federal investigation into the arrest of a student who brought a homemade clock to class that was seen as a possible bomb.

The Texas attorney general's office earlier this month ordered the Irving school district to provide a copy of the U.S. Department of Justice letter to The Dallas Morning News.

Instead, the district on Thursday sued to prevent the release of the multi-page letter.

The district has been turning over sealed documents to comply with the investigation into the September arrest of 14-year-old Ahmed Mohamed. A charge against him was later dropped.

The teen made the clock and brought it to class to show a teacher.