DETROIT (Reuters) - General Motors Co <GM.N> is recalling 50,500 Cadillac SRX luxury crossover vehicles because an airbag might not deploy, possibly leading to injuries to those sitting in the right rear seat.

The recall, announced by GM on Friday, affects 47,401 vehicles in the United States and the rest in Canada and Mexico from the 2011 model year. The U.S. automaker said it knew of no crashes, injuries or complaints related to the issue.

The SRX and the CTS sedan are the top-selling Cadillac models in the United States this year, both with more than 22,000 sales. SRX sales rose 18 percent in the first five months.

GM said the SRX air bags are programed to turn off the right side roof-rail airbag if someone does not sit in the front passenger seat, but the owner's manual says that airbag will deploy whether or not the seat is occupied. If no one is seated in the front passenger side, the roof-rail airbag will not deploy in an accident, potentially leaving rear seat passengers on that side at risk.

The repair entails only a software reprogramming, GM said. It is an issue only in North America because that is where the automatic occupant sensing system is used; exported models use a manual key to disable the passenger side airbag. The key disable system does not suppress the roof rail airbags.

(Reporting by Ben Klayman and Bernie Woodall in Detroit; editing by John Wallace and Gerald E. McCormick)

(This story corrects the description of the potential problem in airbag deployment)