KATY, Texas -

Katy ISD confirmed that a Morton Ranch High School basketball coach is under investigation for having an improper relationship with a student.

The school district began investigating last Thursday after receiving an anonymous letter saying the coach was involved in a relationship with a 16-year-old student.

The coach resigned Monday. Katy ISD isn't releasing his name because of the investigation.

The district released a statement Wednesday that read in part, "At this time, investigators do not believe that the former teacher's alleged actions involve any other students."