Standard & Poor's said the automaker's credit could fall further into junk status due to the “rapidly weakening state” of the global automotive market.
GM shares plummeted $2.15, or 31.1 percent, to close at $4.76 after falling as low as $4.65. That low marked the automaker's lowest trade since March 15, 1950.
The company dismissed speculation that it was headed toward bankruptcy.
A company spokesman said Friday:
Clearly, we face unprecedented challenges related to uncertainty in the financial markets globally and weakening economic fundamentals in many key markets, but bankruptcy protection is not an option.