Ikea has withdrawn meatballs from sale in 14 European countries after tests in the Czech Republic found traces of horsemeat in a batch made in Sweden.
Meatballs from the same batch had been sold in many states, including the UK, France and Portugal, the retailer said.
Swiss food giant Nestle meanwhile said it had found horse DNA in meat from the Spanish supplier, Servocar.
The discoveries come as EU agriculture ministers meet for talks expected to focus on the growing horsemeat scandal.
Since the first horsemeat was discovered in frozen meals and burgers in the UK and Ireland last month, traces have been found in meat products across Europe.
'Testing like mad'
Ikea's announcement on Monday came after the Czech State Veterinary Administration said horsemeat had been found in 1kg (2.2lb) packs of meatballs manufactured in Sweden and shipped to the Czech Republic for sale in Ikea stores there.
A total of 760kg (1,675lb) of the meatballs have been intercepted and stopped from reaching Czech shelves, according to the Associated Press.
Horsemeat had also been found in beef burgers imported from Poland, the Czech State Veterinary Administration said.
In a posting on its Swedish Facebook page, Ikea first confirmed it was halting all sales of meatballs at its stores in the country.
Later, the company announced that meatballs from the affected batch of meatballs had also been sent to Ikea stores in Slovakia, Hungary, France, the UK, Portugal, the Netherlands, Belgium, Spain, Italy, Greece, Cyprus and the Republic of Ireland.
Ikea insisted that it had not found any horsemeat during in-house tests on its own range of food products, carried out two weeks ago, but said new tests would now be carried out.
"We do not tolerate any other ingredients than the ones stipulated in our recipes or specifications, secured through set standards, certifications and product analysis by accredited laboratories," a statement said.
Also on Monday, the Spanish agriculture ministry announced that traces of horsemeat had been found in beef pasta meals produced by brands owned by Nestle.
A statement on the Swiss company's website said it was withdrawing six "La Cocinera" products and one "Buitoni" product from shops in Spain, and that it had halted all deliveries from the meat supplier, Servocar.
Nestle said testing continued across its products, a week after it announced that it was withdrawing two types of beef pasta meals from supermarkets in Italy and Spain which had been supplied by a company in Germany, H J Schypke.
A Nestle spokesman told the BBC the discovery of horsemeat in the products of a second supplier was not an indication that the problem was widespread across the company, but because "we are testing like mad".
The labelling of the origin of meat and the traceability of the products will be high on the agenda at the EU ministers' meeting.
Europe's food retailers depend on a complex network of brokers, cold stores and meat-cutting plants around the continent from which to source the ingredients wherever they are cheapest, says the BBC's Christian Fraser, in Paris.
The evidence of the past few weeks shows that national food safety authorities have failed to identify a problem in the supply chain over a significant period of time, he adds.
While the original agenda of the EU meeting included support for rural communities and the common fisheries policy, it is expected ministers will now try to come up with measures to tackle the horsemeat scandal.
Those could include a pan-European labelling project for frozen food, a move which has the backing of France and Germany.
Paris and Berlin both want compulsory labelling and traceability.
UK Environment Secretary Owen Paterson said on Friday that he would "continue to insist on concrete, co-ordinated action right across Europe when I meet European agriculture ministers on Monday".
But a workable deal could be difficult, our correspondent says. The discovery of horsemeat comes in long, complex and poorly regulated supply chains in the meat industry.
At least a dozen countries are involved in the horsemeat affair, which implicates some of the biggest meat processors and food producers.
Italy joined the list on Saturday, reporting horsemeat in some lasagne products.
On Friday, Germany's consumer affairs ministry announced it had found traces of horse DNA in 67 of 830 food products tested.
Irish authorities on Friday suspended production at one processing plant after horsemeat was found labelled as beef.