EXCLUSIVE

The L.A. County Dept. of Children and Family Services is concerned about the well-being of Blac Chyna and Rob Kardashian's baby ... so much so they've gone to court to make sure she's protected.

TMZ has learned the Dept. has gone to L.A. County Dependency Court so a judge can determine if Dream is safe.

Sources familiar with the case tell TMZ, DCFS opened an investigation involving Chyna's alleged drug use, and this was before Rob and Chyna split up.

As we reported, Chyna has obtained a restraining order against Rob after claiming he beat her.