LONDON -- After disappearing briefly from public view, the scandal over horse meat sold as beef re-emerged on Wednesday with an alert over 50,000 tons of meat sold across Europe and an earlier recall of a product in Britain containing a veterinary drug banned from the human food chain.
The Dutch food safety authority said it was trying to trace meat sold to 130 companies in the Netherlands and 370 in 15 other countries, including France, Germany and Spain. The Dutch suppliers of the meat were unable to say where the 50,000 tons in question originated, said Tjitte Mastenbroek, spokesman for the Netherlands Food and Consumer Product Safety Authority.
"There is no specific indication that this is a danger to the public,'' Mr. Mastenbroek said, ''but the company cannot give the origin of the meat, so we cannot give a guarantee."
The food safety authorities in the 15 countries have been notified about the concerns, and the Dutch companies that bought the meat will be asked to remove it from sale if it can still be traced. The two Dutch meat suppliers were named as Wiljo Import en Export B.V. and Vleesgroothandel Willy Selten B.V.
Late Tuesday in Britain, the Asda chain, which is owned by Walmart, announced a recall of Smart Price Corned Beef. The product was withdrawn from shelves in March after it was found to contain traces of horse meat, and further tests showed that the banned drug, known as bute, had been detected in very small doses, the company said.
"Asda is recalling this product and anyone who has Asda Smart Price Corned Beef should not eat it," said a statement on the company Web site, which added that the risk to health was extremely low. Consumers were asked to return the product to stores.
The announcement is a new development in the scandal over horse meat in beef products, ranging from frozen lasanga to Ikea's Swedish meatballs. UntilTuesday, there had been no suggestion that any item sold in Britain posed a health risk.
Eight horses slaughtered in Britain for human consumption tested positive for bute, and although some of that meat was exported to France, none of it was used in British food, according to the authorities.
Tests to detect bute take longer than those for horse DNA, which is why the Asda product was withdrawn from shelves last month well before the discovery of traces of bute that prompted the recall.
A second Asda corned beef product that also contained horse meat traces and had been taken off supermarket shelves is also being recalled as a precaution, although no bute has been discovered, the company said.
In Britain, the Food Standards Agency said Asda's corned beef contained "very low levels" of bute, four parts per billion, and was the only meat product in which bute had been found. The level of bute found in the corned beef is "considerably lower" than the highest levels found in horse carcasses, 1,900 parts per billion, the agency said.
The agency cited previous comments from the chief medical officer for England, Sally Davies, in which she said that horse meat containing phenylbutazone presents a very low risk to human health.
"Phenylbutazone, known as bute, is a commonly used medicine in horses," she said. "It is also prescribed to some patients who are suffering from a severe form of arthritis. The levels of bute that have previously been found in horse carcasses mean that a person would have to eat 500 to 600 100 percent horse meat burgers a day to get close to consuming a human's daily dose. And it passes through the system fairly quickly, so it is unlikely to build up in our bodies."
"In patients who have been taking phenylbutazone as a medicine, there can be serious side effects but these are rare. It is extremely unlikely that anyone who has eaten horse meat containing bute will experience one of these side effects."
But Mary Creagh, the environment spokeswoman for the opposition Labour Party, said it was "deeply worrying that bute, a drug banned from the human food chain, has been discovered in one brand of corned beef."
"This product was withdrawn from sale on March 8 yet has only been formally recalled now, after testing positive for bute, meaning people could have unwittingly been eating meat containing this drug for the last month.
"This exposes the weaknesses in the government's handling of the horse meat scandal where products were withdrawn but in some cases not tested either for horse meat or bute. The interests of the consumer should have been put first."
The British food industry has tested around 5,400 beef products and about 1 percent showed traces of horse meat.
Correction: April 10, 2013, Wednesday
This article has been revised to reflect the following correction: An earlier version of this article misstated the day that Asda said it had withdrawn its Smart Price Corned Beef from supermarket shelves. It made the statement late Tuesday, not late Monday.
This article originally appeared in The New York Times.