It started swirling through the markets early in the morning. One trader after another passed it on, irrespective of whether there’s any truth to it: Warren Buffett, they said they had been told, was apparently interested in buying a stake in General Electric Co.

Hours later, there was still zero indication that the speculation was anything beyond just that, but the market reaction was real: Shares in the faltering industrial powerhouse soared as much as 6.4 percent, the biggest one-day advance since October 2015.

The stock closed up 4.27 percent, at $13.44. A day earlier, the shares fell to the lowest since July 2009.

For beleaguered investors, it was, if nothing else, a welcome reprieve from what’s been a brutal 15-month stretch of grim news, from tumbling demand for GE’s gas turbines to a probe of the company’s accounting by the US Securities and Exchange Commission. That’s made GE the worst performer on the Dow Jones industrial average since the end of 2016, wiping out almost $168 billion in shareholder value in the process through Monday.

The sudden increase Tuesday is because of market chatter that Buffett will take a position, said Nicholas Heymann, an analyst at William Blair & Co. “It may be a plausible theory, given Buffett had recently spoken to the press that he might be interested in GE at the right price,’’ he said by telephone.

GE declined to comment. Buffett’s Berkshire Hathaway Inc. didn’t immediately respond to a request for comment. Buffett, who rode to GE’s rescue during the 2008 financial crisis, said earlier this year that he would consider an investment in the company or its assets if the price was right.

Buffett has been an investor in GE before. He helped inject capital into the industrial giant during the crisis by buying $3 billion in preferred shares, and received a common-stock holding once some warrants expired years later. Berkshire has mostly sold that stock, Buffett said in February.