How soon can mom get prego again after having babies?

I am fostering a mom and 3 kittens who are about 9 weeks old now. We rescued them from a sewage plant 3 weeks ago. The mother has gotten noticably fat and somewhat firm around the middle. She also is annoyed by her children and hiss at them when they get near her.

I have no experience whatsoever in pregnant cats, so I don't even know what to look for. Is it possible that she could even be pregnant? How soon after giving birth can a cat get pregnant again?

She can pretty much get pregnant again right away.

Ya I dont think cats even wait! I know the male cat will sometimes kill kittens to put the mommy back in heat. Is there a male cat who isn't nuetered there?

Cats can get pregnant while nursing kittens! I'd take her to the vet and verify is she's pregnant again. It can cause problems with both the kittens (not enough food) or mom in having litters one on top of another.

Can this cat be spayed now?