An American flag has been torn to shreds at a Utah high school and replaced with an ISIS flag in what authorities suspect is some kind of sick prank.

Employees at Hurricane High School in southwest Utah discovered the vandalism early on Thursday morning. In addition to the flag, someone had spray painted 'ISIS IS COMI' on a wall.

Investigators with the Hurricane Police Department sent images of the flag to the FBI for analysis.

'Based on information we received from the FBI we do not believe this act was perpetrated by someone linked to the Islamic State,' the department said in a statement.

Someone spray painted 'ISIS IS COMI' on a wall outside Hurricane High School in Utah early Thursday morning. The graffiti was quickly removed by school district employees

The flag pole in front of Hurricane High School is seen in a file photo. Vandals removed the American flag and replaced it with an ISIS flag early on Thursday

The graffiti, which looked like someone was interrupted while writing 'ISIS is coming', was swiftly removed by Washington County School District employees.

Workers also lowered the ISIS flag immediately and replaced it with a new American flag.

The shredded American flag was discarded at the scene, and is being processed for physical evidence to see if any clues lead to the perpetrator.

Police said they were following several leads but had not yet made an arrest in the case.

An ISIS flag is seen being removed in Tabqua, Syria in April. An FBI analysis of the flag raised at Hurricane High School indicated that it was not authentically linked to ISIS

Classes at Hurricane High School were held as usual on Thursday, and school was also scheduled as normal on Friday.

'We do not believe there is a danger to students or teachers at the school,' local police said.

'Hurricane Police Department has a full time School Resource Officer on site and additional officers will be present to ensure students and faculty feel safe.'

Hurricane High School is a public high school with a student body of roughly 770.