Students in Minneapolis schools are awaiting the all-clear following a district-wide lockdown ordered this morning in response to a tip from Minneapolis police that threats had been posted on two social networking sites.

The threats did not target a particular school, so district administrators ordered all buildings locked and identification checked on anyone leaving or entering. District officials don't know how the threats came to the attention of the police.

Parents were notified of the lockdown via an automatic calling system. Additional notices will be sent as information becomes available and parents will be told when the potential threat is resolved.

Elementary-level pupils will remain in their classrooms until police have more information. High school students may move from class to class but must otherwise stay at their desks.

District spokeswoman Emily Lowther said Minneapolis police are keeping the district abreast of developments in the investigation.