CHICAGO (Reuters) – The U.S. government plans to issue new guidelines for food companies as early as this week after an increase in recalls of meat and poultry products possibly containing metal, plastic and other foreign materials, a food-safety official said on Monday.

The U.S. Department of Agriculture (USDA) will advise foodmakers to start internal investigations when they receive customer complaints and to notify the government within 24 hours if contaminated products are in the marketplace, Carmen Rottenberg, administrator of the USDA’s Food Safety and Inspection Service, said in an interview.

The voluntary guidelines, in the works for months, are designed to ensure companies meet pre-existing regulatory requirements, she said.

USDA records show that since the beginning of 2018, Tyson Foods Inc, Smithfield Foods Inc and other companies have launched more than 25 recalls involving millions of pounds of chicken nuggets, calzones, sausages and other foods that potentially contained dangerous materials.

Consumer advocates say increased automation in meat processing plants has contributed to more machine parts breaking off and contaminating food. The meat industry says producers are reluctant to recall food until they investigate whether consumer complaints about foreign objects are legitimate.

Multiple consumer complaints have often preceded recalls, the USDA said in the agenda for a monthly meeting that two consumer advocates provided to Reuters last week.

In an interview to answer questions about the meeting agenda, Rottenberg said recalls may have increased because the USDA has put more focus on ensuring that food companies and government inspectors know the requirements for recalling products.

The new guidelines will advise foodmakers on how to investigate and process complaints and apply information from them to subsequent reports of contaminated products, she said.

“Taking very prompt action is what’s really critical to the agency,” Rottenberg said.

A trio of recalls of Tyson Foods, Perdue Foods and Pilgrim’s Pride Corp chicken products that may have contained rubber or wood put a spotlight on food-safety risks in January and February.

Perdue launched an investigation that did not conclusively determine how wood may have ended up in its chicken nuggets, spokesman Joey Shevlin said. The company subsequently made changes and keeps wood away from unpackaged products on its manufacturing floor, he said.

In a separate recall on Feb. 23, frozen food maker Bellisio Foods said there may have been pieces of glass or hard plastic in Boston Market brand barbecue pork prepared meals. The recall affected about 173,376 pounds of products.

On Saturday, privately held Agri Beef recalled about 30,260 pounds of ground beef products produced in its Washington Beef facility in Washington state. Two days earlier, a consumer complained about finding blue plastic in a product, according to the company, which said it was auditing its procedures to prevent future contamination.

“Foreign matter contamination, it’s a reflection on something going awry in the inspection process and the quality control process of a company,” said Thomas Gremillion, director of food policy for the Consumer Federation of America.

Representatives for Pilgrim’s Pride, JBS, and WH Group’s Smithfield Foods did not respond to requests for comment. Tyson said instances of foreign materials in its products were rare.

“If they happen we move quickly to notify those affected and take corrective action,” Tyson spokesman Worth Sparkman said.

The North American Meat Institute, an industry group that represents Tyson and other companies, in August published its best practices for handling customer complaints about foreign materials in meat and poultry. The USDA reviewed those recommendations.

“Frankly a lot of consumer complaints are bogus,” said Mark Dopp, senior vice president of regulatory and scientific affairs for the group. He said companies often need time to analyze the veracity of complaints before taking action. Technology also helps meat companies detect foreign materials in food before it is shipped to consumers, according to the meat institute.

Rottenberg said food companies must alert the USDA quickly if they receive customer complaints, which sometimes come with photos of meat and poultry products containing foreign materials.

“Companies know whether there’s a legitimate concern or whether someone’s taking a picture of something that never could have been in their product,” she said.

Tony Corbo, a senior lobbyist for Food & Water Watch, said recalls have ticked up partly because more food in meat plants is being prepared by machines with parts that can break off.

“Obviously the agency is starting to see that this is an alarming trend in terms of all these recalls,” Corbo said.