I agree with Michelle. Doing investigation regarding this matter would be of great help to identify the reason why your child's been having bruises. I do understand that at this stage, babies can get into accidents because of they are hyperactive--they can crawl around and touch and pull/push stuff that might cause them harm. Either way, the teacher/staff should be keeping an eye all the time. And they should've informed you beforehand if they see some bruises or if they knew that you're child got hurt. They shouldn't be giving you answers like they are not sure what happened or what causes the bruises because that means that they are not fully monitoring your child (as well as the other babies in the infantcare).
If the person in charge of my child is unaware of my child's well-being, I will take appropriate action immediately and not leave room for ambiguity. It is unacceptable for him or her to be oblivious to how my child could possibly be bruised. At the very least, they should have information on possible reasons and be helpful instead of defensive. If it were me, I'd take my child elsewhere and make sure the school is aware of the situation so it doesn't happen again to any child.
I think you should speak to the Principal. Find out whether the centre has CCTV and demand to see the past videos of the day your baby came back with bruises. Bruises are very unusual for a 9 month old baby. I really hope the centre will be open minded and objective here. You can also choose to make a police report and inform ECDA (the governing body for infantcares).
Absolutely talk to the principal about this, ask for reports, photos, CCTV footage. If there are no reports and no conclusive evidence, it means that the school is not attentive enough nor is it caring for its students enough. If they had noticed it, they should have come to you first about it. You can always leave and find a new school!
This is not acceptable. Talk to the principal and if they do have a cctv, have a look at it. if they do not wish to comply you could report to the police for an investigation, but you should be ready to switch to another childcare.
Bring it up with the head of the school. Principal etc. Ask for CCTV to replay. Straight up no bullshit. This is your kid's well being. Have no mercy in your pursuit for the truth, but have leniency when deciding who to blame.
Do take this up asap with the centre's in-charge. This sounds like a serious problem taking place.
thanks