A masked person with a semiautomatic gun entered the office of a San Fernando Valley elementary school Wednesday morning and then fled when staff called police, officials said.

Officers sealed off a two-block area around Van Nuys Elementary School and began a search within the perimeter that continued into the afternoon, Los Angeles Police Department spokesman Richard French said.

The person fled in the direction of a nearby church school after leaving the elementary school, French said.

There were no reports of any shots fired, he said.

A Van Nuys Elementary School staff member reached by phone said the school was locked down, but would release no other information.

A telephone message seeking comment was left with the Los Angeles Unified School District police force.