I need advice on my cat kittens?

Im really upset right now. My cat I raised sensei found her as a wild kitten, ended up pregnant and she had her kittens under the house. They are about three weeks or a little older now. Well yesterday morning I went outside and I found two of the kittens killed. It was very heart breaking. I tried everything I could to get under the house to save the rest. I could hear them meowing so I know more was still alive. But I couldn't get under the house. This morning a found another died kitten. I started digging to get under the house but still can't. I can't hear the kittens meowing either. But the mother still keeps going there. Do u think she moved them.