The Wage & Hour Division of the US Labor Dept. will sort this out. There are cases that have gone through the court for precedent. The US Fair Labor Act (1938) states wages earned must be paid on a timely basis by the employer. Since some of these workers had over 10 years on the job, it is obvious the company should have known. Why didn't a routine audit pop this up for the company? Because the company knew is an accepted legal argument. The workers will get paid plus a penalty!
http://www.dol.gov/whd/flsa/The full amended Labor Act:
http://www.osha.gov/pls/epub/wageindex.download?p_file=F15794/FairLaborStandAct.pdf