Child Protective Services at Charlie Sheen's

The L.A. County Department of Children and Family Services (DCFS) paid a visit to the home of Charlie Sheen and Brooke Mueller last night.

Mommy, Daddy -- am i safe to live here, no seriously

Sources tell us the visit was triggered by Pitkin County Department of Social Services -- which has an active investigation following the Christmas Day incident between Charlie and Brooke.

We're told Pitkin -- which services Aspen -- wanted to observe the children but they were in Los Angeles. After some squabbling over whether the kids should come back to Aspen, Pitkin officials contacted DCFS in L.A. and asked them to pay a visit.

Last night's visit was not an emergency -- we're told it's just when DCFS was able to get out and see the kids.

We're also told DCFS will take over the case because the kids are now living in L.A.