Toyota Motor Corp (7203.T) is recalling 637,000 vehicles in the United States as part of a massive expansion of a global recall to replace potentially defective air bags that could rupture and send shrapnel into occupants.

The vehicles are being recalled in three separate campaigns, according to documents posted early Friday by the National Highway Traffic Safety Administration.

The air bags were supplied by Japan's Takata Corp (7312.T). More than 36 million vehicles equipped with Takata air bags and sold by 10 manufacturers have been recalled worldwide since mid-2009.

Earlier this week, Toyota in Japan said it would expand its global air bag recalls by nearly 5 million vehicles.

As part of that effort, Toyota is recalling 300,000 vehicles sold in high-humidity U.S. states and territories, including the 2005-2007 Corolla, Corolla Matrix and Sequoia, 2005-2006 Tundra and 2005-2007 Lexus SC, as well as the 2005-2007 Pontiac Vibe made for General Motors Co (GM.N).

Toyota is also recalling 177,000 2003-2004 Tundra and 2004 Sequoia, as well as 160,000 2004-2005 RAV4.

With all of the recalls, NHTSA said "the inflator could rupture, with metal fragments striking and potentially seriously injuring" vehicle occupants.

In a statement, Toyota's U.S. subsidiary said "multiple investigations into the root cause of the potential for inflator rupture are taking place."