Jaime Pressly's Home Alarm Not On, $30k Stolen

Jaime Pressly did not have her burglar alarm on when burglars hit Friday night, and they made off with $30k in jewelry ... TMZ has learned.

We broke the story ... Jaime was the latest celeb to be hit in L.A. -- other victims include Kendall Jenner, Yasiel Puig and Alanis Morissette.

The thieves got in by breaking a window, but we're told the security company never called the cops and therefore they believe the alarm wasn't on.

Jaime discovered the burglary when she returned home after an evening out.