- to place something under lockdown
- to place something on lockdown
Do these two mean exactly the same thing?
BREAKING NEWS: FHS sophomore charged with attempted murder in high school stabbing - Tri City Tribune
The campus was placed under lockdown and the police and emergency personnel responded to the scene.
Brownsville Student Shot By Police Dies | KRGV.com | CHANNEL 5 NEWS | Breaking News Breaking Stories
The campus was placed on lockdown and law enforcement officers were called to the campus.
Yes, they mean the same.
You can also use 'in lockdown'.