TMZ has learned that the Los Angeles County Department of Children and Family Services (DCFS) has received numerous phone calls to their hotline ... about Britney Spears!

Sources tell TMZ that the Child Protection hotline received calls on Brit's kids and her recent bizarre behavior. The DCFS provides a 24/7 phone number that any resident in the Los Angeles area can use to report or discuss any issue regarding children.

Britney Spears entered a rehab facility earlier this week, and as TMZ first reported, she checked out and flew back and shaved her head. Then she checked into a second facility, Promises in Malibu, on Tuesday ... and out on Wednesday!