Looks to be made here in Wisconsin. This is what I found online:
Natural Wood Bedding For Animals
Marth natural wood bedding is manufactured using rigorous quality control standards. Our bedding is made from 100% virgin wood particles from only Marth-approved mills. Shavings are kiln dried to a moisture content of 10% or less and screened to limit as much dust as possible promoting animal respiratory health. The final product is compressed tightly filling plastic bags for easy handling.
The material is an appropriate blend of pine, aspen, and other white soft woods
They say the material is mostly pine and aspen but also other white soft woods and here in Wisconsin it could be birch--I would contact the company to find exactly what kind of other white soft woods to make sure they are chin safe.