Health officials in the United Kingdom and across Europe are scrambling to find out why traces of horsemeat have been found in a wide array of products sold as 100 percent beef. Fingers have been pointed and blame thrown in every direction as this complex investigation into the food supply chain continues to expand.

On Jan. 15, officials from the Food Safety Authority of Ireland published a statement that traces of equine DNA had been found in 10 beef burger products supplied to the grocery store chains Tesco, Lidl, Aldi, Dunnes Stores and Iceland. Horsemeat accounted for 29 percent of the meat content in Tesco Everyday Value Beef Burgers and between 0.1 and 0.3 percent in other beef burgers. Some samples also tested positive for pig DNA.

The samples containing horsemeat came from two processing plants in Ireland, Silvercrest Foods and Liffey Meats, and the Dalepak Hambleton plant in Yorkshire, England. Officials from Silvercrest Foods and Dalepak, subsidiaries of the ABP Food Group, stated that they’d never bought horse product and launched an investigation into two European suppliers.

The grocery chains affected immediately pulled 10 million suspect burgers off their shelves, and other companies whose burgers weren’t tested also withdrew products as a precaution. On Jan. 17, the ABP Food Group suspended work at its Silvercrest Foods Plant in County Monaghan, Ireland, until further notice.

Fast-food chain Burger King, which was supplied burgers by the ABP Food Group, switched to another supplier as a precautionary measure, but on Jan. 31, the company revealed that independent testing showed trace levels of equine DNA in samples taken from the Silvercrest plant. However, Burger King officials said no traces of horsemeat had been found in restaurants.

In early February, two more meat-processing plants found equine DNA in their supply. Production at Rangeland Foods in Ireland was suspended after 75 percent equine DNA was found in raw ingredients and 80 percent equine DNA was found in frozen meat at the Freeza Meats Company in Northern Ireland.

Irish authorities believe some “filler product” made from horsemeat and beef found in contaminated burgers came from Polish suppliers, and as a result, the department of agriculture in Ireland took more than 130 samples of burgers and ingredients from the Silvercrest facility.

On Feb. 6, concerns were raised about French food supplier Comigel’s Findus beef lasagna. Britain’s Food Standards Agency revealed that some Findus UK beef lasagnas contained up to 100 percent horsemeat. Tesco and Aldi immediately removed meals produced by Comigel from their shelves.

U.K. authorities believe either gross negligence or criminal activity may be to blame and have ordered food companies to test their beef products for authenticity. The deadline for the first round of testing is Feb. 15. Comigel supplied products to 16 countries. Companies supplied by Comigel in Sweden and France have recalled multiple meat products, and some grocery chains in the Netherlands have pulled lasagna brands from their shelves as a precaution. European Union officials plan to meet in Brussels, Belgium, to discuss the issue on Feb. 13.

While Europe is generally known to have a good regulatory system for food safety and traceability, the scandal has created public unrest in England and Ireland, countries not known for consuming horsemeat.

Concern has also been raised about the possibility of some horsemeat containing phenylbutazone, which isn’t allowed in animals meant for slaughter since it poses a human health risk. In 2012, the FSA found nine cases where horses slaughtered for human consumption in the United Kingdom tested positive for bute, but so far, no bute has been found in any meat tests by the FSAI.

As of Feb. 11, the FSA has mandated that all horses slaughtered for human consumption must test bute free before entering the food chain.

The British Horse Society released a statement, stating that the horsemeat scandal has highlighted concerns about meat traceability and equine welfare.

One of those concerns is the 2012 decision of the Department for Environment, Food and Rural Affairs to withdraw funding from the National Equine Database, a public website used to track horses in the United Kingdom with a passport that contains details of the drugs the horse receives in its lifetime. Started in 2008, the NED closed in August, unable to continue without funding.

Without a central database to facilitate medication checks on horses, some horses could be medicated but still be passed as fit for consumption.

“The British Horse Society neither condones nor encourages the consumption of horse meat and believes it is a choice for the individual. However, we as a nation must recognize the origin of much of the horsemeat produced in our country. Rather than coming from animals ethically raised specifically for the purpose it tends to come from horses that are surplus to requirements; a direct result of Britain’s equine overpopulation problem,” read the statement.