The outcome of three months of checks for horse DNA and the anti-inflammatory drug bute in processed food are expected today.
The regime of the investigation was agreed by EU ministers in February, including 2,500 random tests on processed food for horse DNA and 4,000 for bute.
The move comes as the Government announced it was launching a wide-ranging review into the horse meat scandal to restore consumer confidence in the food they buy.
The results of the investigation are expected to be declared in Brussels, at 11am UK time.
One hundred kilograms (220lb) of horsemeat imported from Hungary and labelled as beef has been identified in Lancashire, with 40kg of it already sold to the public, the Food Standards Agency said.
Supermarket chain Aldi has announced that a random sample of its 'Oakhurst Frozen Meatloaf' had been found to contain horsemeat.
An Aldi spokesman said: "Aldi has been contacted by the FSA to alert us that a random sample of our Oakhurst Frozen Meatloaf tested by a local authority has been found to contain horse meat.
"We are surprised and deeply disappointed at this news. Our DNA testing, carried out last month in accordance with FSA guidance, also tested samples of this product and found it to be clear of horse meat.
"The product is not part of our main range of everyday products and was stocked on a limited availability basis. However, we have immediately withdrawn any of the remaining stock from our stores.
"We will continue to test products and if we have any reason to believe the meat content is not correct, we will continue to act immediately in the interests of our customers."Customers can return the frozen meatloaf to their nearest Aldi for a full refund."
More than half of consumers have changed their shopping habits as a result of the horsemeat scandal, a survey for consumer group Which? has found.
It also found that public trust in the food industry has dropped by 24%, with 30% of those polled now buying less processed meat and a quarter (24%) buying fewer ready meals with meat in or choosing vegetarian options.
The results of the survey comes as supermarket giant Tesco announced it had withdrawn a line of its frozen meatloaf after tests revealed it contained between 2% and 5% horse meat.
Populus surveyed 2,064 UK adults online between February 22 and 24.
Many of the UK's biggest food firms and supermarkets have recalled beef products since January after tests found they contained horse DNA.
A first wave of tests found horse DNA in products including Aldi's special frozen beef lasagne and special frozen spaghetti bolognese, Co-op frozen quarter-pounder burgers, Findus beef lasagne, Rangeland's catering burger products, and Tesco Value frozen burgers and Value spaghetti bolognese.
A second wave of tests revealed contamination of Asda's chilled beef bolognese sauce, beefburgers, minced beef and halal minced beef sold by Sodexo, which supplies food to schools, care homes and the armed forces, and a Whitbread Group lasagne and beefburger.
The third round of tests revealed contamination of Bird's Eye Traditional Spaghetti Bolognese and Beef Lasagne, Taco Bell's ground beef and Brakes' spicy minced beef skewer.
Furniture retailer Ikea also withdrew wiener sausages in the UK last month after tests found "indications" of horsemeat, and it also withdrew a batch of its traditional meatballs.
The company said it was removing the sausages from sale in Britain, France, Spain, Ireland and Portugal after tests confirmed "a few indications of horse meat".
Tesco has withdrawn its 'Tesco Simply Roast Meatloaf' from sale after it tested positive for between two and five per cent horsemeat. It is the fourth Tesco-branded product to test positive for horsemeat.
Tim J Smith, Tesco Group Technical Director, said: "Today we have withdrawn from sale a product which has tested positive for between two and five percent horsemeat.
"The product is a frozen Tesco Simply Roast Meatloaf 600g. The product tested was manufactured between October 2012 and January 2013 at Eurostock in Craigavon, Northern Ireland.
"Tests on 15 other lines from the same manufacturing site were clear of horsemeat. Our investigation to thoroughly understand the source of the contamination has started and we will complete our investigation before deciding whether to continue using the supplier.
"As part of our new DNA testing programme we have now tested more than 500 products identified as being most at risk of containing horsemeat. This is the fourth Tesco-branded product to have tested positive.
"We are very sorry that we have had a further product which has failed to meet the high standards we and our customers expect."
The Food Standards Agency will publish the results from the first wave tests for horsemeat in retailers, food chains and catering companies that supply schools across the UK.
The tests come after traces of horsemeat were found in school meals served by Leicestershire County Council.
- Leicestershire County Council supplies 224 schools across the county
- The council has confirmed there is no health risk to pupils
- A second item tested, a beef grill steak, was found to contain no trace of horse DNA and has been reinstated on menus
Horsemeat has been found in minced beef served in school dinners in Leicestershire. Leicestershire County Council says tests show the beef contained less than 1% trace of horse DNA and has been permanently removed from school menus:
We want to reassure parents that there is no health risk and that we're satisfied with the quality of all the beef products we serve.
The vast majority of food we supply is Red Tractor-assured and we will continue to regularly seek assurances from our school food suppliers to ensure that they comply with legislation.
McDonald's has confirmed tests for horsemeat in its products came back negative.
Jill McDonald, the president and chief executive of McDonald's UK, said:
We voluntarily provided samples of all beef burgers currently available on our menu to the Food Standards Agency (FSA) for their own tests.
All tests, including our own, have now been completed and we can confirm that no horsemeat has been found in any of McDonald's products.
Our beef supply chain is short and transparent and has just five simple steps from the farms through to the food we serve in our restaurants.