Baby bitten at nursery 3 times in 2 days

Hi everyone, I have a 10 month old daughter who has been at nursery full time for a month now. Before that she went for half a day a week for 2 months to get her settled. Well, on Wednesday I got a phone call saying that she had been bitten twice by the same little boy and could I sign an accident form. The first time he bit her finger while she was stood at a baby gate. The second she was playing at the play kitchen, he walked over and wanted her to move (she can't walk yet but has been walking on furniture for 2 months now) but she couldn't move fast enough so he bit her on the arm. They put a cold compress on it and she calmed down. They told me the boy who did it is a known biter and they are working with the parents regarding the biting. Well she went to nursery today (friday), she doesn't go on Thursdays, and we have just bathed her and noticed a big bite mark on her back! Nothing was mentioned at pick up, I had no phone call either. They must not have seen it happen. At pick up they said she had been smiling and happy all day, but surely she screamed when she was bitten?

I'm unsure where to go from here. I'm furious they clearly weren't watching carefully enough, but also that they didn't keep the two apart as they have two rooms. I'm unsure this third bite was the same child but I feel like she must be his target now!