St. Louis Blues -- Heavy Security Presence ... In Wake of Ferguson Clashes

There's a heavy police presence at the St. Louis Blues hockey game Tuesday night -- with officials making sure fans feel safe amid the insanity in neighboring Ferguson ... TMZ Sports has learned.

We spoke with staffers at the Scottrade Center -- who tell us there is "about double" the amount of security at the arena ... most of which are off-duty cops privately hired to work the event.

It's the first major sporting event in the area since the grand jury in the Mike Brown case announced it would not be indicting Officer Darren Wilson.

FYI -- there are roughly 2,200 National Guard troops in Ferguson to help maintain the peace.

Don't forget, there were clashes outside of the St. Louis Cardinals games back in October when protesters and Cards fans faced off over the issue.