Call CPS and give them specifics.
Even if it turns out not to be true (or as true as you think) you should still call.
Someone called CPS on us recently – my son convinced someone at school that he had no clean clothes (he did and does but he throws them on the floor so the dogs sleep on them), there was no food in the house (he meant there are no chips or ice cream, just gross stuff like apples, eggs, sandwich makings, spaghetti, cereal, and so on), we beat him (actually he hits my husband to try to get out of taking his meds) and that there are drugs in the house (well, yeah – he takes anti-psychotics, his dad is a diabetic with multiple problems, and I take thyroid medicine so we do have prescription drugs in the house, but nothing even remotely recreational).
The CPS guy came out to the house and took pictures of the food in the pantry, the clean clothes in the dryer, and the the mess that my son calls his room, and left smiling. As he pointed out, our son was abusing us, not the other way around, so there was nothing he could do because he is charged with protecting children, not their parents.
The only one that was really upset was my teenaged daughter because he came to her school and asked her questions about stuff that was none of his business, like about drugs and just stuff!
In our case it was untrue, but I can’t fault the person that called. If it had been true then a child could have been in danger.
So call, but bear in mind that specifics are a great help to them – tell them how the child is being abused and how you know; recount specific instances where you have witnessed abuse, with dates, times and locations if possible. They are a branch of law enforcement and the justice system so they need evidence and concrete examples.
Good luck!