Securities regulators on Tuesday issued a joint alert warning investors against buying or retaining over-the-counter shares of the now-bankrupt General Motors Corp.

The alert, sent out by the Securities and Exchange Commission and the Financial Industry Regulatory Authority, said there is "widespread misunderstanding by investors" that the stock in the bankrupt GM company is related to the "new" General Motors Co. that emerged from bankruptcy last week as a new entity that will belong in part to the U.S. and Canadian governments.

"Motors Liquidation Company and the 'new' GM are separate and distinct," the alert said. "The new GM currently has no publicly traded securities, and none of Motors Liquidation Company's publicly owned stocks or bonds are or will become securities of the new GM."

The alert added that "Motors Liquidation Company is currently winding its way through bankruptcy court - and there is a real possibility that stock holders will receive nothing from these proceedings."

Finra, the self-regulatory group for the brokerage industry, halted over-the-counter trading in old GM stock under the GMGMQ ticker symbol last Friday. A new ticker symbol - MTLQQ - will be issued for the old stock to avoid having it confused with the new GM, which does not have any publicly traded securities. Over-the-counter trading using that new ticker symbol is slated to resume Wednesday.

The SEC and Finra both said that bankrupt companies like GM have often been the subject of rumors about stock tips.

"Unfortunately, investors may have received confusing, potentially misleading, information about the old GM," the alert said. "As recently as last Friday, newsletters and other promoters have touted the purchase of the stock."

The alert added that investors are often confused by the fact that a company's securities may continue to trade after bankruptcy even though the common stock of that company is likely to be cancelled.

"When a company files for reorganization under the federal bankruptcy laws, investors are often tempted to buy or hold the company's common stock," the alert said. "The reality is, however, that when companies emerge from bankruptcy, the common stock of the 'old' company is usually worthless."

-By Sarah N. Lynch, Dow Jones Newswires; 202-862-6634; sarah.lynch@dowjones.com