All after-school activities at Horizon High School were canceled on Thursday because of security reasons.

Just before 2 p.m. school officials received “several tips regarding various potential safety situations that are unrelated to one another at our school,” said Principal Kim Brady in a statement to students and parents.

Horizon, an Adams 12 Five Star School at 5321 E. 136th Ave. in Thornton, also received a security tip Thursday morning.

“As a precaution, we also implemented several additional security protocols including additional police presence in the school,” the statement said.

An investigation is ongoing. “The reason after-school activities have been canceled is to allow law enforcement and district security to continue the investigation,” the statement said.

Students and their families will be notified Thursday evening about the situation and about school operations Friday.