DETROIT--General Motors (GM) says the troubled mortgage industry and frozen credit markets have raised doubts that the mortgage business of its GMAC financial arm can survive.

The automaker said Monday in a filing with the Securities and Exchange Commission that market developments have raised substantial doubt about the viability of Residential Capital LLC.

The filing says that the value of Residential Capital's mortgage loans have deteriorated due to weak housing prices, delinquencies and defaults. It is also having trouble raising capital.

GM owns 49% of GMAC LLC.

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GM also said in the filing that Delphi Corp., its former parts-making operation that was spun off in 1999, may not be able to emerge from bankruptcy protection.

GM shares fell 93 cents to $3.43 after sinking as low as $3.02.