Lab puppy poop in crate.

Hi guys, I have a 19 weeks old female lab whose has been with me for about 4 weeks. Initially, she has no problem sleeping in her crate at night for about 5-6 hours. But recently she started to defecate in her crate. I always feed her early and take her out many times before I put her in her crate. And still she would poop in her crate. Any recommendations how to fix this problem? Thanks in advance.