Three students who were arrested for allegedly planning to carry out a pre-Christmas break attack on students and staff at a southeast Iowa high school had access to guns and communicated through coded letters, an official said Wednesday.

While the students had access to the weapons, they had not taken any action to secure them for an attack on Central Lee High School in Donnellson, said Jim Sholl, chief deputy for the Lee County sheriff's office.

He said the guns belonged to the students' parents and had not been moved from where they were being stored in their homes.

The student's coded letters used symbols and needed a legend or key to decipher, Sholl said.

The students were arrested early Tuesday after one of them went to the principal late Monday afternoon to alert him of the attack, which allegedly was to have been carried out Tuesday or Wednesday.

Jacob Schulte, 15, Dalton Bird, 17, and Stephen Copeland, 16, were charged Tuesday with conspiracy.

Schulte and Bird remained in custody Wednesday at a juvenile detention center. Copeland, the student who came forward, was released to his grandmother, Sholl said.

In the coded letters, the students named two students believed to be the focus of the threat, Sholl said. He said a teacher was only identified as a substitute.

He declined to say whether he believed the students would have carried out the attacks.

"I'm not going to say anything that could jeopardize the investigation or prosecution of the case," Sholl said. "But I don't think law enforcement, or society, can stop and wonder if this is joke or how serious it is. We better deal with this from the start in a serious manner. It's easier to apologize later for a mistake than deliver death messages because we didn't do enough."

He declined to discuss a possible motive.

John Henriksen, Central Lee superintendent, said investigators were conducting interviews Wednesday with students at the high school, which has a student body of about 350.

Henriksen said the school had experienced disciplinary problems with "one or more" of the students who were charged, but he declined to be more specific. He also said that none of the students were "heavily" involved in school activities.

The school district gave parents the option of keeping their children home Tuesday and Wednesday without it being counted as an absence. On Wednesday, the high school reported just 40 percent attendance, but Henriksen said the day, the last before the Christmas break, had been scheduled as a job fair day at the school.

"So that probably, if this hadn't happened, would have affected our attendance," he said.

Two sheriff's deputies provided extra security at the high school on Tuesday, but the additional security had tapered off to only increased patrols in the school parking lot on Wednesday, said Henriksen, who assured parents the school was safe.

"We're confident because (the sheriff's office) is confident that they've addressed the potential threat," he said.