GREAT FALLS, Mont. (AP) — An Air Force nuclear missile base in central Montana was put on lockdown Thursday following a report of an active shooter, according to authorities.

Malmstrom Air Force Base in Great Falls announced the lockdown in a social media post.

Malmstrom officials are directing people to stay away from a building where a suspected “real world threat” was reported at about 10:30 a.m.

The Great Falls Police Department said it was providing security and support in the area of the base and nearby schools due to “an incident that may be occurring” at Malmstrom.

An advisory to shelter in place was announced for schools in the surrounding community. Police recommended private schools and daycare also shelter in place.