WASHINGTON — MGM National Harbor generated $49.9 million in gambling revenue for the state, or 37 percent of total gambling revenue from the state’s six operating casinos combined.

Total gaming revenue in April was $135.7 million, up almost 31 percent from a year ago, according to figures from the Maryland Lottery and Gaming Commission.

MGM National Harbor opened Dec. 8, 2016.

MGM may also be drawing gamblers away from the state’s other casinos. Maryland Live! at Arundel Mills, now the state’s second-largest casino by revenue, generated $45.3 million last year, down 21.6 percent from a year earlier. Gambling revenue at Baltimore’s Horseshoe Casino was down 18.7 percent from a year ago, to $24.6 million.

At the state’s three smaller casinos, gambling revenue was down at Hollywood Casino Perryville, but rose modestly at both Rocky Gap Casino Resort and Casino at Ocean Downs.

April’s gaming revenue fell short of the record set in March, when Maryland’s casinos generated $141.2 million for the state, up 44 percent from a year earlier and an all-time high.