MARION, Iowa (AP) -

Officials say it's back to business as usual after extra police were called to Linn-Mar High School in Marion after a threat was received.

District officials say Marion police were notified about the threat on Monday, and extra officers were sent to the campus. They've since left.

District officials say social media quickly spread word of the threat.

Neither police nor school officials would discuss the nature of the threat or anything the police investigation has uncovered.