Statute of Limitations for class "B" Felony

I have been arrested on a theft charge from 1997 (arrested 3 plus years after the supposed crime) It is a class B felony and no warrant was in effect just a probable cause order for 3 years. Now I am being charged with 4 counts of First degree theft and have yet to be questioned. What is the Statute of Limitations on a Class B felony in the state of Washington? and how can I be charged with a crime from a probable cause order from 3 years ago with no other evidence being submitted?