Iowa Gov. Terry Branstad called Monday for a congressional investigation into how what he called "a smear campaign" against the meat product commonly called "pink slime" got started.

The company that makes the product, South Dakota-based Beef Products Inc., announced last week that it would stop production at plants in Iowa, Kansas and Texas amid public outcry. There are no precise numbers on how prevalent the product known in the industry as lean, finely textured beef is, but past estimates have ranged as high as 70 percent; one industry official estimated it was in at least half of the ground meat and burgers in the United States.

The phrase "pink slime," coined by a federal microbiologist, has appeared in the media at least since a critical 2009 New York Times report. Celebrity chef Jamie Oliver has railed against it, and it made headlines after McDonald's and other major chains discontinued their use last year.

But a recent piece by The Daily on the U.S. Department of Agriculture's purchase of meat that included "pink slime" for school lunches touched a nerve with Houston resident Bettina Siegel, whose blog "The Lunch Tray" focuses on kids' food. She started an online petition asking Agriculture Secretary Tom Vilsack to halt use of "pink slime" in school food, and the USDA announced last month that starting in the fall it would give schools the option of choosing ground beef that doesn't contain it.

"We have a smear campaign going on against a product that is healthy and safe," Branstad said at his weekly news conference. "If they get by with this, what other food products are they going to attack next?"

The governor said he suggested an inquiry to U.S. Reps. Steve King and Leonard Boswell and raised the issue with Vilsack, a former Iowa governor. King and Boswell did not immediately return messages left Monday requesting comment.

Lean, finely textured beef is made by heating fatty bits of meat left over from other cuts to about 100 F and spinning it to remove most of the fat. The lean mix is then compressed into blocks for use in ground meat and treated with ammonium hydroxide gas to kill bacteria, such as E. coli and salmonella.

"It's clear this is a safe product," Branstad said. "It's a lean product, it helps reduce obesity and there is a spurious attack being levied against it by some groups. You can suspect who they might be. They are people who do not like meat."

Branstad went on the offense last week, discussing the issue at a news conference and touring a Nebraska processing plant with governors from Kansas and Texas and lieutenant governors from Nebraska and South Dakota.

Beef Products' plants in Iowa and Kansas each produced about 350,000 pounds of lean, finely textured beef per day, while the one in Texas produced about 200,000 pounds a day. The shutdown has affected 650 jobs, the company said.

Reports over weekend showed that Beef Products' top executives and workers have given $820,750 to congressional and presidential candidates over the past decade, with all but $28,400 going to Republicans. Branstad, a Republican, received $150,000 over the past two years from people tied to Beef Products, his spokesman Tim Albrecht said Monday.

Branstad said he's firing off a letter to all the other governors in the nation, urging them to be equally aggressive on the issue. He also called on students at agricultural colleges in Iowa to use their social media skills "to counter what Hollywood and the media elites and the people who are spreading this misinformation are doing."

"It's their future that's being threatened by this," Branstad said.