Rescue workers had taken 17 survivors to hospital, but said 32 passengers were still in the wreckage.
Federal Territory Fire and Rescue assistant director Azizan Ismail said: "Our early observations indicate they are all dead,"
Genting Highlands, 34 miles from Kuala Lumpur, has the country's only legal casino.
Meanwhile, a car and a packed church bus returning from an outing collided and plunged into a river in Indonesia's West Java province, killing at least 16 people and injuring more than a dozen others.
The bus, carrying about 60 people from a church in northern Jakarta, was returning from a trip to the hilly resort town of Puncak when its brakes apparently malfunctioned.
Police said the bus hit a small car and crashed through the wall of a roadside building before both vehicles fell into the river.