"There are people who are out there to defraud, who are looking to cheat," Le Foll told RTL radio.
Sorin Minea, who heads Romania's main food producers' association, claimed Monday in an interview that international gangs had perpetrated the fraud. "There is an international ring that does this... the documents (relating to the meat) are changed abroad," he said.
An expert would know the difference between horsemeat and beef and would be unlikely to mislabel it by accident.
"If the buyer is suspicious they have to check it at the source," he said.
Michel Barnier, a former French agricultural minister who now works at the European Union level, said it was not an issue of food safety but of justice.
"Consumers have the right to the truth, quality, and transparence. We have to do more in tracking," he told Europe 1 radio.
Food company Findus Sweden plans to sue France's Comigel for breach of contract and fraud, Findus Nordic CEO Jari Latvanen said.
He said the company's deal with Comigel stipulates that the beef in the frozen lasagna should come from Germany, France or Austria, but that has not been the case.
Associated Press writers Lori Hinnant in Paris, Mike Corder in the Hague, Netherlands and Karl Ritter in Stockholm contributed to this report.