Rio Grande City Grulla ISD increased law enforcement presence at one of its campuses after a threatening message was found in a restroom, the district said.

The message referenced “potential violence” at Rio Grande City High School, the district said. Troopers with the Texas Department of Public Safety and local police officers are at the campus out of an abundance of caution.

“We want to be clear: at this time, there is no identified credible threat to our campus,” the district said in a statement posted on social media. “The writing appears to have been left at an unknown time, and we are working closely with local law enforcement to investigate the matter thoroughly.”

Classes are continuing as normal, the district added.