French food group Danone, which is finalizing a 12.3 billion-euro ($17 billion) agreed bid for Dutch baby-food and special nutrition company Numico, has already acquired 26.4 percent of Numico, regulatory filings showed on Wednesday.

Before Tuesday, when the holding was recorded with the Dutch financial market authority, Danone held less than 5 percent of Numico. Any previous stakes above 5 percent would have to have been registered with the AFM, but there were no such records.

A trader in the Netherlands said that Danone had most likely bought Numico shares on the open market, given the high volumes recorded on Tuesday.

More than 21 million shares in Numico traded hands daily, on average, in the last five days compared with a daily average of 3 million in the last three months, according to Reuters data.

Numico shares traded at 53.75 euros at 0920 GMT on Wednesday, below Danone's indicated all-cash offer of 55 euros per share for Numico.

Danone's offer price is a 44 percent premium over Numico's average share price in the three months prior to the acquisition announcement.

By acquiring Numico, which makes infant milk formula, early food for babies and specialized foods for people with illnesses or medical conditions, Danone said it was aiming to be the world's largest health and nutrition company.

Last week, Danone said it was in exclusive talks to sell its biscuits business for 5.3 billion euros to Kraft Foods Inc., the world's biggest cookie maker.

The Numico deal, backed unanimously by both boards, is expected to result in a definitive agreement within weeks, the companies said when announcing the deal on Monday.