A homemade bomb was discovered this week at a high school in San Jose, sparking an evacuation less than a week after a deadly mass shooting at another California school.

Authorities were called to Oak Grove High shortly before 11.30am on Tuesday after a gardener found the device in some bushes in the student parking lot and took it to the administration building.

Police say an examination of the suspicious item determined that it was a ‘functioning’ improvised explosive device.

Before noon, the campus was placed on lockdown as a precaution, after which the campus was evacuated, with students being led to nearby Coy Park. 

The San Jose Police Department’s bomb squad was brought in and safely detonated the explosive device by 5pm. 

Bomb-sniffing dogs searched the school but found no additional explosives.  

Classes were cancelled on Wednesday but were to resume Thursday morning.

Police say there were no reported threats to the school before the bomb turned up and investigators are trying to determine its origin.

The Santa Clara County and FBI crime labs are assisting with the investigation into the bomb. 

The station KPIX reported, citing unnamed sources familiar with the incident that the explosive device was about the size of a cellphone and was wrapped in tape. 

It was described as having what appeared to be a fuse coming out of the top, and it may have contained some kind of a liquid.  

East Side Union High School District Superintendent Chris Funk spoke critically of the gardener’s decision to not only touch the suspicious device he found in the bushes, but also to bring it inside the school building.