(CBS/AP) Investigators disclosed Sunday that meat cut from a Holstein sick with mad cow disease was sent to four more states and one territory than previously believed.

However, Dr. Kenneth Petersen, an Agriculture Department veterinarian, said the meat was safe. “The recalled meat represents essentially zero risk to consumers,” he said.

Petersen said investigators have now determined that some of the meat from the cow slaughtered Dec. 9 went to Alaska, Hawaii, Idaho, Montana and Guam. Earlier, officials had said most of the meat went to Washington and Oregon, with lesser amounts to California and Nevada, for distribution to consumers.

He stressed, though, that the parts most likely to carry the infection — the brain, spinal cord and lower intestine — were removed before the meat from the infected cow was cut and processed for human consumption.

Although federal officials maintain the food supply is safe, they have recalled as a precaution an estimated 10,000 pounds of meat from the infected cow and from 19 other cows all slaughtered Dec. 9 at Vern's Moses Lake Meat Co., in Moses Lake, Wash.

Petersen, of the department's Food Safety and Inspection Service, said the department still is recovering meat and won't know if all of it has been returned until later this week.

Officials say the slaughtered cow was deboned at Midway Meats in Centralia, Wash., and sent Dec. 12 to two other plants, Willamette Valley Meat and Interstate Meat, both near Portland, Ore.

Petersen has said that much of the meat is being held by those facilities.

Petersen said Willamette also received beef trimmings — parts used in meats such as hamburger. He said those trimmings were sold to some three dozen small, Asian and Mexican facilities in Washington, Oregon, California and Nevada.

In response, representatives from supermarket chains in the West —
Albertsons, Fred Meyer, Safeway and WinCo Foods — have voluntarily removed ground beef products from the affected distributors. Safeway has said it will look for another supplier.

Mad cow disease, known as bovine spongiform encephalopathy, is a concern because humans who eat brain or spinal matter from an infected cow can develop variant Creutzfeldt-Jakob disease. In Britain, 143 people died of it after an outbreak of mad cow in the 1980s.

Despite assurances that meat is safe, Japan, the top importer of American beef, and more than two dozen countries have blocked U.S. beef imports. Jordan joined the list on Sunday. U.S. beef industry officials estimated this week that they've lost 90 percent of their export market. Ranchers export 10 percent of the beef they produce.

U.S. agriculture officials arrived Sunday in Japan to discuss maintaining beef trade even as the United States investigates how the Holstein in Washington state got mad cow disease.

Dr. Ron DeHaven, the department's chief veterinarian, said on Saturday that investigators have tentatively traced the first U.S. cow with mad cow disease to Canada. This could help determine the scope of the outbreak and might even limit the economic damage to the American beef industry.

The tentative conclusion traced the diseased cow to the province of Alberta, where Canada had found another case of mad cow infection last May.

However, DeHaven re-emphasized Sunday that investigators aren't certain of that because U.S. records outlining the animal's history do not match ones in Canada. Canadian officials had complained it was premature to reach any firm conclusion.

DeHaven said Sunday that DNA tests were being arranged to help resolve the matter.

Canadian papers show the cow had two calves before it was exported to the United States, contrary to U.S. documents which classified the animal as a heifer when it arrived, meaning it had never born calves.

Also, according to Canadian documents, the diseased cow was 6½ years old — older than U.S. officials had thought. U.S. records say the cow was 4 or 4½ years old.

Officials are concerned about the cow's age because it may have been born before the United States and Canada in 1997 banned certain feed that is considered the most likely source of infection.

A cow gets infected by eating feed containing tissue from the spine or brain of an infected animal. Farmers used to feed their animals such meal to fatten them.

The Food and Drug Administration is trying to find out if the cow ate contaminated feed — a difficult task because the animal may have gotten the disease from feed it ate years before it appeared sick. The disease has an incubation period of four or five years.

Dr. Stephen Sundlof, head of the FDA's Center for Veterinary Medicine, said an animal could get sick if it ate a tiny bit of infected brain or nervous system material, as little as half a gram.

But officials are less certain about how much would infect a human. “It's not known what dose would infect humans, but it would be higher for humans than for cattle,” Sundlof said.

Investigators have considered other ways the disease could spread. Although scientists have never found a case of mad cow infection being passed from a mother cow to its calf, they want to test the sick cow's calves for the disease as a precaution.

Sen. John Kerry, a candidate for the Democratic presidential nomination, proposed on Sunday several changes to the system of monitoring livestock in response to the discovery of mad cow disease in the United States.

Kerry's plan calls for a national tracking system, a sharp increase in the testing of cattle for the disease and an unspecified level of financial aid to farmers who stand to suffer as a result of the discovery.

Since the announcement that a now-slaughtered Holstein cow from Washington state was sick with mad cow disease, more than two dozen countries have halted imports of U.S. beef, valued at $3.4 million a year.

“The current mad cow investigation underscores the urgent need for a national system to make diseased livestock easier to track and contain,” Kerry, a Massachusetts senator and one of nine candidates for the Democratic presidential nomination, said in a statement Sunday.

Kerry said downed animals — those too sick or injured to stand or walk unassisted — that are being tested for the disease should not be processed until the results are known.

In the Washington state case, the sick cow was slaughtered and its meat distributed 13 days before preliminary tests confirmed the presence of bovine spongiform encephalopathy, which is known as mad cow disease.

“It's common sense, if a cow is suspect it should be tested and the results should be back before it is processed and in the food supply,” Kerry said in Iowa, where the Jan. 19 precinct caucuses launch the presidential nominating season and the cattle industry is a significant force in the state's economy.

Kerry also called for a national system to track the movement of livestock, and a sharp increase in Agriculture Department testing of cattle for the disease. Over nine years, only 30,000 of the 300 million cattle slaughtered have been tested for the disease, he said.

Another element of his proposal is a ban on the sale of the brains and vertebrae of cattle, the portions of the animal affected by the disease. Kerry also called for “fair and equitable” financial assistance for those hurt by the crisis, including farmers, but did not say how much money they should be given.

In an interview with The Associated Press last week, former Vermont Gov. Howard Dean said he favored a tracking system that would let the government quickly track the origins of the sick cow, quarantine all animals it came in contact with, and assure the marketplace that the rest of the meat supply is safe.

Dean also said he supported federal financial assistance for the cattle industry.

Missouri Rep. Dick Gephardt on Saturday criticized President Bush for refusing to pay for country-of-origin labeling for meat, and for ignoring the Agriculture Department's and the Food and Drug Administration's need for more money to inspect agricultural imports.