BOOM! CLAP! The Sound of the Nuthouse Goes On and On and On and On
The Owosso Argus-Press, October 6, 1931
Keyword searches are everything on Google News. Eloise + Gruber returned this short snippet concerning a bomb explosion in the tunnels in October of 1931. While I haven't been able to track down any further information, Dr. Gruber, at the time suspected it was a dynamite or a nitro-glycerine explosion caused by a fanatic or a disgruntled employee.
Detroit Free Press, October 6, 1931
Although this subsequent article in the Detroit Free Press doesn't add much insight into the matter it clarifies a few things on an otherwise insignificant event. Though a further bomb plot would be discovered just a few weeks later involving two Communist charges from the institution. I will be updating that in the near future and will link to the new posting when it is completed.