A 21-year-old sorority sister at the University of Mississippi was found dead near a lake over the weekend — and foul play is suspected, authorities said.

The body of Alexandria “Ally” Kostial was discovered Saturday morning during a routine patrol in Harmontown, about 20 miles from the Ole Miss campus in Oxford, according to the Lafayette County Sheriff’s Department.

“It is apparent that foul play was involved,” a Lafayette County Sheriff’s Department spokesperson said.

Her father, Keith Kostial, said she was taking summer courses and teaching fitness classes at the time of her death.

“We were visited by the Sunset Hills MO Police who communicated to us that our beautiful dear Alexandria (Ally) Kostial was the victim of a homicide,” her father wrote Sunday on Facebook. “As of now, it is believed the crime happened in Lafayette County, MS.”

It’s unclear what caused her death, but the case is under investigation.

“This is an active investigation so details are no being released,” Lafayette County Sheriff’s Office said.

The student, who was from St. Louis, Mo., was working toward a bachelor’s degree in marketing and set to graduate next year, news station KMOV reported.

School officials confirmed her death Sunday in a statement.

“We are truly saddened by the death of Alexandria Kostial,” said University of Mississippi Interim Chancellor Larry Sparks.

“Ally was a valued member of our campus community. We extend our deepest sympathy to her family, friends, and classmates and stand ready to support them during this time. We appreciate the work of the Lafayette County Sheriff’s Department and Coroner as they conduct their investigation.”

Kostial’s sorority sisters in the university’s Alpha Phi chapter paid tribute to her on social media.

“She was the brightest light and always had a smile on her face. She truly was a ray of sunshine,” friend Kassidy Desnoyer wrote on Facebook.