I Suspect My Son’s Non-profit Little League Directors Are Embezzling Money

I have been coaching in my son’s little league for 8 years. There has always been a suspicion that money is being embezzled. I recently found out I can access their tax returns and my suspicions grew much more. A business that made well over $220,000 yet only around $2,000 in profit. Some years claiming very high loses. The league doesn’t pay rent on the space they use and nearly everyone from the coaches to field maintenance are supposedly volunteers. Only expenses would be umpires and some field maintenance equipment, dirt etc. I know there are certainly expenses to run a LL, but these seem outrageous. The directors claim they get paid nothing for their “hard work” yet find time to be at the field daily(I don’t know what they do for actual work). It seems like someone is getting paid under the table. I can see the numbers, but not the receipts. What can I do to look into this further and possibly get rid of those who are stealing?

Edit: when I say the director is at the field daily - I should have mentioned they are using the clubhouse as a personal office for their business. A reason to add to my suspicion that money is being moved around improperly.