Shares of Bloom Energy Corp. /zigman2/quotes/209802424/composite BE -0.50% plunged 22% toward a record low, after short seller Hindenburg Research said it had uncovered an estimated $2.2 billion in undisclosed serving liabilities. "Bloom's tricky accounting allows it to mask servicing costs and shift write-downs to other periods, thereby avoiding recognizing major recent additional losses," Hindenburg wrote in a research note. "We believe that large debt maturities in 2020 and 2021, amounting to nearly $520 million, make Bloom Energy an obvious bankruptcy candidate." Bloom was not immediately available to comment. Hindenburg said that, once touted as the prospective "holy grail" of clean energy, Bloom's technology is "not sustainable, clean, green or remotely profitable." The stock is now trading at about 22% of its initial public offering price of $15. The company went public in July 2018, with the stock rising to a record close of $35.80 in September 2018. Last month, the stock had plummeted 43% after Bloom reported fiscal second-quarter results that beat expectations but provided a downbeat outlook. The stock has tumbled 67% year to date, while the S&P 500 /zigman2/quotes/210599714/realtime SPX +0.48% has gained 20%.