The soldier, identified as Christopher Dombroski, 20, was last heard from at about 8:30 p.m. Sunday.
The Capitol Forest is a 91,650-acre state forest in Thurston and Grays Harbor counties that is managed by state Department of Natural Resources. It is used for logging and recreational activities, including off-road motorcycling, mountain biking, horseback riding and hiking.
It is criss-crossed with trails and nearly 600 miles of gravel road.
This is a developing news story. More information will be posted as it becomes available.