British officials held an emergency meeting Saturday in London. Participants agreed "meaningful results" must be achieved by Friday, UK Food Standards Agency spokesman Brad Smythe said.
Officials discussed what tests are possible, what laboratory capacity is needed, and what can be done to protect consumer confidence, he said.
The evidence so far suggests "either criminal activity or gross negligence," Environment Secretary Owen Paterson said, adding that "more bad news" could come.
UK food businesses have been ordered to test all processed beef products for authenticity and report back to the authorities by Friday.
"I am determined that we get to the bottom of this and that any wrongdoing discovered is punished," Paterson said in a statement.
Prime Minister David Cameron weighed in Friday on Twitter. "This is completely unacceptable -- this isn't about food safety but about proper food labeling and confidence in retailers," he wrote.
Legal action under way
Latvanen credits his company with uncovering "a serious case of fraud."
"What has happened with Comigel is a crime, a scandal," he said in an interview with CNN.
While Findus has begun legal action in Sweden, Findus France previously said it will file a legal complaint Monday against a Romanian business that is part of the supply chain. It did not name the business publicly.
"There are two victims in this affair: Findus and the consumer," Findus France said in a statement.
The British arm of Findus said it is considering legal action against suppliers as well. Early results of an internal investigation "strongly suggest" the horse meat contamination of a beef lasagna product "was not accidental," the company said.
Tests showed up to 100% horse meat
Aldi said tests on random samples demonstrated that the withdrawn products contained between 30% and 100% horse meat.
"This is completely unacceptable and like other affected companies, we feel angry and let down by our supplier. If the label says beef, our customers expect it to be beef."
Samples of the affected Findus lasagna contained between 60% and 100% horse meat, according to UK and Irish food safety inspectors.
In January, the Food Safety Authority of Ireland found that 10 out of 27 hamburger products it analyzed in a study contained horse DNA, while 23 of them -- or 85% -- tested positive for pig DNA.
In nine out of the 10 burger samples, the horse DNA was found at very low levels, the inspectors said. But in one sample from Tesco, Britain's largest retailer, the horse meat accounted for about 29% of the burger.
Tesco apologized and vowed to make sure it never happens again.
Irish officials blamed ingredients from Poland.