Officials evacuated Countryside High Monday morning after they received two online warnings.
Clearwater Police spokesman Rob Shaw said police received this direct message on the department's Facebook page: "Countryside high school 4/9/18 school shooting/bomb 10:30."
Shaw declined to say who sent the message but said police are investigating the sender. The message, which could be perceived as a warning or a threat, was not believed to be sent by a student. But it prompted an evacuation of the school Monday morning, which lasted until about 11:30 a.m.
Clearwater Police conducted a sweep of the school "in an abundance of caution," and did not find anything. Students returned back to class.
School district spokeswoman Lisa Wolf said the school resumed normal operations, however additional law enforcement officers remained on campus for the rest of the day.
School officials also were made aware of a Snapchat message that mentioned "CHS" "going out with a bang." It said "don't go to school tomorrow," but the threat is believed to originate out of Clover, N.M., and was already deemed unfounded by police.
Countryside High, at 3000 SR 580 in Clearwater, has a student enrollment of about 1,900.