PITTSBURGH — Kraft Heinz disclosed an investigation by federal regulators and said it will slash the value of its Oscar Mayer and Kraft brands by $15.4 billion, major setbacks for a company trying to revitalize its stable of household-name brands.

A wave of bad news, which also included a dividend cut and a weak outlook for the year, sent shares plunging 26 percent at the opening bell Friday, their largest decline in a single day. Before noon, the company had lost $16 billion of its market value. At market's close, the stock was down 27.4 percent at $34.95 a share.

The company's bad day was felt by other iconic food brands on the stock exchange; Orrville-based J.M. Smucker Co. closed down 5 percent to $101.42 per share, with losses also for Campbell Soup (7.3 percent), Kellogg (2.7 percent) and General Mills (0.8 percent).

Kraft Heinz cited the impairment charge for a stunning $12.6 billion fourth-quarter loss.

Kraft Heinz said the investigation by the U.S. Securities and Exchange Commission is related to its accounting practices in the division that handles interactions with suppliers. The SEC declined to comment.

The steep write-down and loss in the quarter is a devastating recognition that efforts to change the trajectory of the company have not been as successful as once thought.

Kraft Heinz and other food makers that dominated grocery shelves for much of the post-World War II era have been whipsawed by a seismic shift in what consumers want.

Families, particularly in the U.S., have pivoted away from familiar packaged foods amid a proliferation of products marketed as being more wholesome, or that promise new tastes. The trend hasn't been good for some of Kraft Heinz' standbys like Jell-O and Kool-Aid and Oscar Mayer hot dogs.

In the fourth quarter, Kraft Heinz said lower prices in the U.S. helped boost sales volume. Its overall global sales also edged up, but its profit when excluding one-time charges still fell short of Wall Street expectations.

The tie-up of Kraft and Heinz was engineered in 2015 by Warren Buffett's Berkshire Hathaway and 3G Capital. The Brazilian investment firm is known for taking over companies and improving results by slashing costs.

But the strategy apparently didn't work as planned at Kraft Heinz.

"We were overly optimistic on delivering savings that did not materialize by year end," said Kraft Heinz CEO Bernardo Vieira Hees. "For that, we take full responsibility."

JPMorgan analyst Ken Goldman said the results cast doubt on 3G Capital's strategy of chasing growth by cutting costs.

"Investors for years have asked if 3G's extreme belt-tightening model ultimately would result in brand equity erosion," Goldman wrote.

Goldman said the answer may be in the $15 billion intangible asset write-down for the Kraft and Oscar Mayer brands.

As for the SEC investigation, Kraft Heinz said the subpoena prompted it to launch its own review, which resulted in a $25 million charge for expenses that should have been accounted for previously. The company said it is working to prevent similar mistakes.