Christopher Dorner

Christopher Jordan Dorner (February 6, 2013)

Five Irvine schools increased police presence Thursday in response to an online manifesto allegedly posted by an ex-LAPD officer saying he would harm law enforcement members and their families.

Five students at the campuses are possibly related to Christopher Dorner's potential targets, Irvine Unified School District Supt. Terry Walker said in a prepared statement.

"Again, please know that the schools themselves are not targets, and no student has been specifically named," Walker said in his statement. "Only individuals associated with the former officer's dismissal have been reported as potential targets."

The students attend Irvine and Woodbridge high schools, Lakeside and Venado middle schools, and Stone Creek Elementary School, where extra police will be present out of what Walker called an abundance of caution.

In Newport Beach and Costa Mesa, campuses operated normally. A school official said the district was not aware of any dangers that would require additional security Thursday.

"We continue to work closely with both the city of Newport Beach and City of Costa Mesa on any threats, and plan accordingly," Newport-Mesa Unified School District spokeswoman Laura Boss said.

An Irvine police spokeswoman said officers in the city were also avoiding motorcycle duty as a safety precaution.

A statewide manhunt for Dorner, who is wanted for at least three slayings, is underway.

He is suspected of killing Monica Quan, 28, an assistant women's basketball coach at Cal State Fullerton, and Keith Lawrence, 27, a public safety officer at USC. The engaged couple were shot multiple times Sunday in their car in the parking garage of their Irvine condominium complex.

Dorner is also suspected of shooting three police officers in Riverside County, killing one, early Thursday morning after Irvine police named him as a suspect.

Police say the manifesto threatens more than two dozen people, including law enforcement officials who made the decision to fire him for making false statements about his training officer.

jeremiah.dobruck2@latimes.com

Twitter: @jeremiahdobruck