GRASS VALLEY – Four people were detained after Nevada Union High School was placed on lockdown on Thursday afternoon, the Nevada County Sheriff's Office said. 

Shortly before 12:45 p.m., deputies said they received reports that a person had a firearm near the school. 

After arriving on the scene, four "persons of interest" were detained for questioning, the sheriff's office said. 

The school was placed on lockdown due to its proximity. That lockdown, as well as a lockdown at Echo Ridge Christian, was lifted shortly before 2 p.m., deputies said. 

No injuries or gunshots have been reported, deputies said. At this time, deputies have not said if a firearm was located. 

The investigation is ongoing. 

• Grass Valley
• Nevada County