Cheerios and Yoplait maker General Mills Inc. missed analysts' estimates for quarterly sales and margins on Tuesday, hurt by higher input costs and lower demand for its snacks and yogurts in the United States.

The Minneapolis-based company's shares (GIS) were down 7.9 percent, leading a 2.2 percent decline in the S&P 500 Packaged Food & Meats index.

General Mills, which also owns the Nature Valley cereal bar and Annie's yogurt brands, said sales in its U.S. snacks unit fell 4 percent, while yogurt sales declined 2 percent. The company's stock has lost more than a fifth in value this year.

"There was a bit of a step back in sales momentum so you're seeing some of the bears jump on that and wondering if things aren't progressing as well as we thought they were," Edward Jones analyst Brittany Weissman said.

The packaged goods industry has been battling surging freight and commodities costs all year as railroads and truck fleets hike rates.

This hurt General Mills' first-quarter adjusted gross margin, which fell 160 basis points to 33.6 percent in the quarter. Margins were also weighed down by a charge related to the acquisition of Blue Buffalo Pet Products Inc. Analysts at J.P. Morgan called the results "less than ideal," saying the company's gross margin was far lower than expected.

Some of the gross margin pressure will continue into the second quarter but is expected to ease off later in the year, helped by higher prices, better placement on shelves and more premium products, Chief Financial Officer Donal Mulligan said in an interview. Mulligan added that lower supply chain costs were also expected to help margins.

"We came into this year knowing we were going to see higher inflation, like the rest of the industry and our retail partners," Mulligan said.

Rival cereal-maker Kellogg Co said last month that transportation costs were up strong double digits and that this would be the case for the foreseeable future.

Net income attributable to the company fell to $392.3 million, or 65 cents per share, in the quarter ended Aug. 26. Excluding items, the company earned 71 cents per share, beating the analyst estimate of 64 cents.

The company's net sales rose nearly 9 percent to $4.09 billion, boosted by its acquisition of pet food company Blue Buffalo, but missed analysts' estimates of $4.12 billion, according to Thomson Reuters I/B/E/S.