French police are searching several sites run by dairy group Lactalis as part of an ongoing investigation into a baby milk scare.
More than 12 million boxes of powdered baby milk have already been recalled in 83 countries following a salmonella outbreak.
Lawsuits have been filed by parents who say their children became unwell after drinking the formula.
Sites raided include a factory in Craon, north-western France.
The factory was closed last month after it was thought the contamination started in one of its drying towers.
Lactalis spokesperson Michel Nalet confirmed that police had visited the Craon factory.
"As we have said before, Lactalis is co-operating with justice authorities and will provide everything necessary for a smooth conduct of the investigation," he told AFP news agency.
Dozens of police were also seen entering the company's offices in nearby Laval, French media report.
Reuters news agency, citing a source close to the investigation, reports that officers are carrying out "technical searches for data and documents" for clues on how the contamination occurred.
At least 37 babies are so far reported to have been affected in France, with one case reported in Spain and a further unconfirmed case in Greece.
In France, 18 of the infants taken ill were said to have required hospital treatment. All are recovering well, according to AFP, which cites France's public health agency.
What does the company say?
The Lactalis group, which is one of the world's largest producers of dairy products, has said it believes the contamination was caused by renovation work at its Craon factory.
In a recent interview in French newspaper Journal du Dimanche, chief executive Emmanuel Besnier denied the firm had attempted to hide the outbreak.
He also promised the company would compensate any families affected.
Lactalis has annual sales of €17bn ($21bn; £15bn) and has 246 production sites in 47 countries and employs 15,000 people in France alone.
What products are affected?
The Picot, Milumel, Celia and Taranis brands have all been recalled.
Last week a company spokesman told the BBC that all the countries affected had been informed, in Europe, Asia, Latin America and Africa. The UK, US and Australia were not affected, he added.
What are the dangers?
Salmonella can cause diarrhoea, stomach cramps, vomiting and severe dehydration. It can be life-threatening, especially in young children.
The illness, caused by intestinal bacteria from farm animals, is dangerous for the very young and elderly because of the risk of dehydration.
The government crackdown
France's agriculture minister said products from the Craon factory will be banned indefinitely while the investigation is still ongoing.
The French government has warned the company it must expect penalties over its handling of the affair.
It also threatened to impose sanctions against retailers last week, after it emerged that several major supermarket chains had continued to sell products that could have been contaminated.
What about the victims?
On Monday, a meeting was held between the government and an association of victims' families.
It came after Mr Besnier said that Lactalis had offered to compensate all of the affected families.
The association's president, Quentin Guillemain, said the company "fell far short of expectations" in dealing with the outbreak and controlling the distribution of contaminated products.
"We still don't know where they are, we don't know if they have been destroyed or if they've been drunk," Mr Guillemain said.
Following the meeting, Mr Guillemain told reporters that "a certain number of families will file complaints in the coming days" but did not specify how many.