Police and school safety officers patrolled three public school campuses Tuesday in response to a written threat, but classes continued as usual and no incidents were reported.

The threat, received Monday, named Campbell High, Castle High and King Intermediate schools. It was a written threat that applied to all three schools, according to Derek Inoshita, communications specialist for the state Department of Education.

“We don’t have much more information than that,” Inoshita said. “HPD is on campus and they are stepping up their monitoring and patrols.”

Police are investigating the situation as a case of terroristic threatening, but declined to release further details. First-degree terroristic threatening is punishable by up to five years in prison and a fine of $10,000.

“We’re not commenting on the nature of threats,” said Michelle Yu, spokeswoman for the Honolulu Police Department. “If anyone has information, please contact CrimeStoppers or HPD.”

Principals at the three schools posted letters on their websites alerting parents of the situation and the security response, and noting that classes and activities would continue as usual.

“At Castle High School, the safety and well-being of all students, staff and families is of paramount importance to us,” Principal Bernadette Tyrell wrote in a letter dated March 7. “Castle administration was made aware of an alleged threat to the school late today. In response to the alleged threat, additional security staff will be monitoring and patrolling the campus.”

She continued: “There will be no changes to the school schedule. We are working closely with Honolulu police and have also consulted with the Hawaii State Department of Education’s Safety and Security Branch to make sure the campus remains safe.”

Monday’s threat was similar to one received Friday, Inoshita said. In that case, students were locked in their classrooms for about an hour as a precaution at Campbell High; Ilima Intermediate; and Kaimiloa, Pohakea and Ewa Beach elementary schools.

On Jan. 28, nine public and private schools in Honolulu were evacuated after a series of telephoned bomb threats were received at about 2 p.m. In some cases, classes were already over and students had left. The schools were Assets School; Maryknoll School; Damien Memorial School; Farrington, Kaimuki, Kalani, Radford and Moanalua high schools; and Washington Middle School.

No arrests have been made in any of the cases, Yu said Tuesday.