A school security officer first reported finding the messages during the last school period on May 23.

Two messages were found on school property, one on the west exterior wall of the annex building, another on a sidewalk along South 200th Street.

School and police officials could not comment on what the messages actually said.

"There was graffiti writing left on the wall to indicate that a shooting would occur at the school today," said Commander Kevin Tucker with the Des Moines Police Department.

"There was the increased security and that has been a very strong presence," said Catherine Carbone Rogers, spokeswoman for the Highline School District.

Four patrol officers from the police department were at the school on May 24 around 2 p.m. Earlier in the day six officers were on the campus, said Tucker.

Two school security officers, and a district security officer were also at the school, said Carbone Rogers

Students were made aware of the situation the day the messages were found and a letter was sent home to parents, she added.

Officers spent the day talking with students between classes to gather information and walking the campus, "just creating a high visibility," said Tucker.

"The main thing is that 99 times out of a hundred these kind of things are hoaxes, but we want to take any kind of threat seriously and make sure that we have the highest security level possible," said Carbone Rogers.

"It is typical that we put more patrol in the area and follow up more leads with the detectives," said Tucker.

There were no immediate leads as to who wrote the messages.

Compiled by Sara Loken