As soon as you feel that something fishy is going on with your employer, start documenting everything. Save copies of emails and memos. Logs, timesheets, post-it notes, or phone calls, anything that relates to the fishy-ness. Even conversations, make a note, put down who was there, witnesses, and what was said. Keep this all at home in case you are ever locked out of the office.
If you file a complaint with any Department of Labor or other regulatory organization you will have a much higher chance of getting a positive outcome if you have evidence to back up your claims and trying to recreate this evidence days, weeks, or months after meetings or conversations, can be difficult.
Be careful about recruiting others in your office to do the same. They may be your friend now, but if their job is on the line they could quickly change their tune and back the employer in an effort to save their job or even promote.