The Massachusetts Gaming Commission has fined MGM Springfield $18,000 following three separate “unacceptable failures” that led to people under the age of 21 being allowed to gamble and, in one instance, being served alcohol, the commission’s top investigator said Thursday.

A 17-year-old was able to spend about two hours on the casino’s gaming floor and was served a complimentary alcoholic beverage on Dec. 25 after security officials at an entrance to the gaming area failed to ask for an ID when the teenager entered, Investigations and Enforcement Bureau Director Loretta Lillios said.

When the teen attempted to cash out, the cage cashier alerted security and the teen was removed from the casino.