It was only a matter of time before the broadening global pet food contamination scandal spread to human food. Now it has done so and the Food and Drug Administration (FDA) has opened a criminal investigation after reports that more than 100 hogs were given contaminated food and later wound up on dinner tables.

The hogs were slaughtered in California's Central Valley after eating feed that contained rice protein tainted with melamine, the industrial chemical that has sickened and killed dogs and cats around the world.

People who bought pork from the American Hog Farm in Ceres, Calif., between April 3 and April 18 are being advised not to eat the meat, although California health officials said there have been no reports of illness in either people or the hogs. Authorities are trying to track down all the purchasers.

"The risk is minimal, but the investigation is very early on," said Kevin Reilly of the California Department of Health Services.

Stephen Sundlof, director of the FDA's Center for Veterinary Medicine, said criminal charges are a possibility, although it is no yet known if there was any criminal intent.

Earlier, federal officials said ingredients imported from China -- and used in the more than 100 brands of recalled pet foods -- may have been intentionally spiked with melamine to boost their apparent protein content.

There are also reports from South Africa that suggest a third pet food ingredient -- corn gluten -- was tainted with melamine. The FDA, however, said that tainted ingredient has not been found in the United States.

Rice protein concentrate
Source: Binzhou Futian Biology Technology, Ltd. Web site

"Melamine was found ... it would certainly lend credibility to the theory that it may be intentional," Sundlof said. "That will be one of the theories we will pursue when we get into the plants in China."

But U.S. Senator Dick Durbin said China has blocked the FDA's efforts to inspect the facilities that manufactured these melamine-tainted ingredients. He and Congresswoman Rosa DeLauro (D-CT) on Wednesday sent a letter to the Chinese Ambassador to the United States urging his country to immediately issue visas to U.S. food inspectors.

"It is unacceptable that the Chinese government is blocking our food safety inspectors from entering their country and examining facilities that are suspected of providing contaminated pet food to American consumers," Durbin said.

Tests revealed melamine in both wheat gluten and rice protein concentrate -- imported from China -- used in the pet foods linked to scores of kidney illnesses and deaths in dogs and cats across the country.

Almost a dozen companies have found that they have used melamine-contaminated ingredients from China in their animal foods, either wheat gluten, corn gluten or rice protein concentrate. In the United States, more than 60 million containers of cat and dog food have been pulled from the market in the past five weeks.

FDA Shields Some Companies

It's not only China that's not being entirely forthcoming.

The FDA said it knows of five companies that received the contaminated Chinese rice protein concentrate. Three firms have identified themselves by announcing recalls; the other two are not publicly known because the FDA will not name them until the companies come forth voluntarily.

Blue Buffalo Recall

Meanwhile, another pet food maker recalled some of its products on Thursday after discovering melamine in one of its ingredients.

The Blue Buffalo Company of Wilton, Connecticut, recalled one production run of its Spa Select Kitten dry food.

"We have taken this action because the rice protein concentrate used for this one production run was obtained from Wilbur-Ellis, the same company who supplied this ingredient to Natural Balance," the company's President, Bill Bishop, said in a statement on Blue Buffalo's Web site.

Natural Balance recalled its Venison and Brown Rice canned and bagged dog foods, Venison and Brown Rice dog treats, and Venison and Green Pea dry cat food earlier this week after discovering the rice protein concentrate used to make some of these products was tainted with melamine.

Melamine is a chemical in plastics and fertilizers, but is not approved for use in pet or human food, according to the (FDA). Blue Buffalo said it discovered melamine in the rice protein -- imported from China -- that was used in some of its food.

"Test results received late last evening (4/18) indicated that this rice protein concentrate tested positive for melamine," Bishop wrote on Blue Buffalo's Web site. "This is the first and only time our manufacturing partner sourced an ingredient from Wilbur-Ellis, and we had no knowledge that they had imported the ingredients from China."

California-based Wilbur-Ellis said it started importing rice protein concentrate from the Chinese company, Binzhou Futian Biology Technology, in July 2006. That company sent 14 containers holding 336 metric tons of rice protein concentrate to Wilbur-Ellis, which distributed 155 metric tons to date.

Blue Buffalo said it produced 5,044 bags of the Spa Select Kitten dry food in the run it's recalling.

"We were able to prevent the majority (of those bags) from ever entering retail distribution," Bishop said. "We are working closely with our retail partners to remove this product immediately and will be re-stocking the shelves with Spa Select Kitten dry food that was produced without any rice protein sourced from Wilbur-Ellis as soon as possible."

He added: "As a family owned company whose reason for being is to provide cats and dogs with the highest quality natural foods, we are extremely upset by this recall and can't begin to apologize enough to our customers. From our perspective, it is unacceptable to produce even one bag of food with the potential to cause a pet to become ill, and we will further tighten our ingredient sourcing and quality assurance procedures as a result of this incident."

The product code on the recalled bags is "Best Used by Mar.07.08 B."

The company said pet owners should immediately stop feeding their pets any of the recalled food. No other brands of Spa Select cat or dog food -- dry or canned -- are included in this recall.

Pet owners with questions or concerns about the recalled food can contact the company at 1-800-919-2833.

Senate Hearings

Last week, Durbin and Senator Herb Kohl (D-WI) held a special hearing on the pet food recall. The hearing pitted FDA representatives and pet food lobbyists against the bipartisan Appropriations Subcommittee.

"Many cats, dogs and other pets, considered members of the family, are now suffering as a result of a deeply flawed pet food inspection system," Durbin said. "The FDA's response to this situation has been wholly inadequate -- we need to establish standardized inspections, impose penalties on companies who delay reporting health problems and increase communication between the FDA and the state inspectors so that we can catch problems more quickly. These sound like basic steps but the FDA has failed to put them in place."

After the hearing, Durbin told that he is working on legislation to address this problem, but he did not specify the scope of his pending legislative action.

A North Carolina pet owner has one suggestion. She wants pet food manufacturers to be required to disclose the following information:

• The sources of their ingredients, including the country of origin;
• The names of the contract manufacturers for these companies;
• The names of the companies and countries they receive their products from.

"China is one of the most polluted and corrupt places in the world and the thought of any food products coming from there makes me want to gag," pet owner Aleda R. of Durham, N.C. told "There is no accountability."

This pet food debacle has struck a personal cord with Aleda.

"My dog has been eating IAMS dry food," she says. "She is a Chinese Crested, a small dog, who had a physical in October, with no problems. Because of the (pet food) scare, I just had her blood work (done) over again, and she has now experienced some 'off the chart on one of her kidney enzymes.'"

More about the Pet Food Recall ...