HUDSON – A nearly yearlong investigation has resulted in drug trafficking charges against two men. Francis Feliz Mejia, 29, of Roxbury, has been charged with trafficking a Class A substance; trafficking a Class B substance over 200 grams and conspiracy to violate drug laws. Charles Claussen, 33, of Stow, faces charges of trafficking a Class B substance over 200 grams; conspiracy to violate drug laws and possession of a Class E substance.