I second the opinion of the sawdust or fine pine shavings being the culprit. Guaranteed thats what happened. I made the same mistake the other day and lost a one week old baby. Hoping the others make it ok. Was in a rush, out of bedding and put a shovel of pine mini flake on top of the straw I had used the day before...I have since covered that over with some towels. Feel like an idiot.
