Students at Minneapolis South High School were greeted Wednesday with a lockdown when they arrived at their Corcoran neighborhood building. 

Teachers were told before the school day that a note found Tuesday after school prompted the decision to operate with a closed campus.  The nature of the note wasn't disclosed because of what district spokeswoman Rachel Hicks said was a continuing investigation by the district and school.

The lockdown means that students are not issued passes during classes, and can't leave the campus for lunch or during an open hour in their schedule. It usually is declared when the perceived threat is extenral, rather than inside the school. Students were permitted to participate in after-school adult-supervised activities such as sports or clubs.

The school at 3131 19th Av. S. ended last school year with two days of lockdown because of concern by school officials over the safety of students.  That followed the shooting of Roosevelt High School student Trequan Sykes, 16, by South student Malcolm Jackson, also 16.  Jackson was sentenced in July to 26 years in prison.