This question is important, since if you don't have the ownership of those money (they belong to someone else), you can't use them. Only when you have the ownership of those money, you can use these money to buy other things like government bonds and MBS
This question is impossible to answer in any meaningful way.
Money, as it is really used in daily life, is hard to define. If you walk in to a bank and get a loan, say $1000, the bank just adds $1000 to one of your accounts, and adds a new account with negative $1000 in it. Which of those is money? Was anything really created? What was it, and when?
If you withdraw that $1000, that could be the moment that new money is created, because that is when the books no longer balance, and that $1000 is now in circulation. On the other hand, the bank just physically moved ten $100 bills from their cash drawer into your hand. Does this suggest that the actual money that was created is the debt? Still, hard to say.
If your bank was previously at their reserve limit, they now need to borrow more reserves. The fed can snap their fingers and add $100 to your bank's account (and a corresponding negative $100 loan). Is that money? Which one? Is that the moment of creation?
How about when your bank orders physical banknotes to replenish their stock? How about when the paper is actually printed?
In my view, all of those things are money. The money in your account, the negative money in your loan, the physical paper money, the money in your bank's account with their reserve branch, etc. Typically when I have this discussion with academic economists, they pick the one slice of the picture that they prefer, and call that slice "money" and everything else is "money substitutes".
The problem with that approach is that it defines away virtually everything that is actually used as money in practice by real human beings as being something that is not-money. It sure makes the study of economics easier to have careful definitions, but the exercise provides no real insight into how anything actually works.