SunEdison Inc., a leading solar-power company saddled with nearly $10 billion of long-term debt, is at risk of filing for bankruptcy protection, one of SunEdison’s affiliates said Tuesday.

SunEdison also reportedly is being investigated by the Securities and Exchange Commission over whether the company might have overstated to investors how much cash it had on hand in November.

In response to both developments, SunEdison’s already battered stock plunged further to less than $1 a share. The stock fell 69 cents, or 55 percent, to close at 57 cents a share Tuesday. At midday Wednesday, the price per share was 59 cents.

Last July, SunEdison was trading above $31 a share. At that point, SunEdison had a market value of $10 billion; it’s now about $400 million.

Based in Maryland Heights, Missouri, SunEdison provides systems using solar power and other renewable energy. The company also has solar research and development facility in Belmont, California. It also developed wind farms in Maine.

The firm has two so-called yieldcos, TerraForm Global Inc. and TerraForm Power Inc., that raise money from public investors to buy power assets from developers and sell power to utilities to generate steady dividends for those investors.

TerraForm Global, in an SEC filing Tuesday, said SunEdison’s “liquidity difficulties” mean that “there is a substantial risk that SunEdison will soon seek bankruptcy protection.”

SunEdison has yet to report its financial condition as of the end of 2015. Earlier this month, the company delayed filing its full-year results because it found “material weaknesses in its internal controls over financial reporting.”

In its most recent quarterly filing, for the three months ended Sept. 30, SunEdison reported that its long-term debt had swelled to $9.8 billion from $5.9 billion nine months earlier.

On a Nov. 10 earnings call with analysts, SunEdison said it had $1.4 billion of cash. But the SEC is looking into whether SunEdison overstated its liquidity, the Wall Street Journal reported, citing unidentified people familiar with the matter.

Those sources said much of that cash already was earmarked for project construction or debt service and thus couldn’t be accessed by SunEdison, the newspaper reported.

The SEC declined comment, and SunEdison said it was not commenting on either the reported SEC probe or the TerraForm Global filing.

Through the first nine months of 2015, SunEdison posted a loss of $919 million on sales of $1.25 billion.