Multiple campuses across Frisco ISD received threatening emails on Monday, according to a letter sent to parents and staff.

In the letter, Frisco ISD said administrators immediately notified the Frisco Police Department and began safety protocols, placing all campuses in "secure status" as the investigation continues.

What is secure status? 

The district said under secure status, all school instruction continues in the building as exterior doors remain locked. And if any student needs to be released from the classroom, it's in a controlled and orderly manner. 

School officials said they believe Monday's threat is "non-credible at this time." However, as a result of the investigation by the police, the district is asking parents not to send students to campus, and any students who had not arrived were asked to stay home.

Students who are already on campus will remain there until law enforcement advises that the district can resume normal operations. School officials said precautionary checks are being made at campuses identified in the emails. 

"We understand that any report of a threat can be unsettling. Please know that the safety and well-being of our students and staff is our highest priority. Our established safety protocols were immediately implemented and are functioning as designed. Frisco ISD and the Frisco Police Department take all threats seriously and respond promptly," the district said in a statement. 

The district also reminded students and parents that making a threat to schools is a "serious offense under Texas law and can result in severe legal consequences."