The Massachusetts Gaming Commission has fined MGM $100,000 for failing to keep minors away from the gambling area of its Springfield casino.
The fine resulted from 22 documented cases of people under the age of 21 being discovered on the gaming floor during the first two months since the casino opened last August.
MGM did not appeal the fine.
MGM Springfield President Mike Mathis has said there is a zero tolerance policy for minors gambling at the casino.
"And that is something we work on very hard," said Mathis.
Earlier this year in response to the problem, MGM said security officers began conducting more age-verification checks on the gaming floor, more signs indicating age-restricted areas were posted, and a midnight curfew was initiated banning people under age 21 anywhere in the resort complex.