General Electric (GE) is masking the seriousness of its accounting problems, according to a whistleblower who raised red flags about the Bernie Madoff Ponzi scheme. The ailing industrial giant denied the claims, but GE stock plunged.

Accounting expert Harry Markopolos claimed in a report posted online Tuesday that GE has “been running a decades long accounting fraud,” resulting in inaccurate filings with regulators.

The Wall Street Journal, which broke the news, called the report “a mixture of detailed financial analysis and sweeping claims.”

GE called the claims meritless. “The Company has never met, spoken to or had contact with Mr. Markopolos, and we are extremely disappointed that an individual with no direct knowledge of GE would choose to make such serious and unsubstantiated claims. GE operates at the highest level of integrity and stands behind its financial reporting. We remain focused on running our businesses every day, following the strategic path we have laid out,” the industrial giant said in a statement posted to its website.

CEO Larry Culp said in a later statement that “this is market manipulation – pure and simple,” claiming Markopolos’s report contains “false statements.”

Meanwhile, analyst Jim Corridore of CFRA Research reiterated a buy on GE stock in a note Thursday. He cited, in part, “increased openness” in GE’s accounting under Culp after “years of financial opaqueness” under his predecessor.

GE recently posted better-than-expected Q2 earnings. It also announced CFO Jamie Miller is stepping down.

GE Stock Loses Sight Of 200-Day Line

GE stock plunged 11.3% to close at 8.01 on the stock market today, marking its worst drop in 11 years. Shares further undercut the 200-day moving average, falling to their lowest level since Jan. 2.

The relative strength line, which tracks a stock’s performance vs. the S&P 500 index, plunged Thursday, approaching December’s long-term low. The RS line is the blue line in the chart below.

That follows a huge dive in the RS line from early 2016 and, longer term, from the 2001 peak.

GE stock rose modestly in late trade on news that CEO Culp bought 252,000 shares at 7.93 each on Thursday.

Shares of Dow Jones stock and industrial conglomerate United Technologies (UTX) edged up 0.1% Thursday, while Honeywell (HON) and 3M (MMM) traded lower.

GE Insurance, Oil-And-Gas Units Eyed

Markopolos told the Journal he found GE’s insurance unit will need to bolster its reserves by $18.5 billion in cash and faulted how General Electric is accounting for its oil-and-gas business. He estimated the accounting problems amount to $38 billion, or 40% of the conglomerate’s market value at the time.

The Boston-based accounting expert warned the Securities and Exchange Commission about the Madoff investment scheme before it became public, but was ignored.

“Mr. Markopolos said he and his colleagues are working with an undisclosed hedge fund, which is betting GE’s share price will decline,” the report added.

The SEC and Justice Department are probing GE accounting of its insurance and power units. The company has denied accounting fraud in response to lawsuits and has mulled switching from long-time auditor KPMG.