NEW YORK (Reuters) -Investment firm TOMS Capital Investment Management has taken a "significant" position in U.S. multinational food manufacturing company Kellanova ( K ) and is engaging with the company, two sources familiar with the matter said on Thursday.

The size of TOMS Capital Investment Management's stake could not be learned and it is unclear what the investment firm and the company, which has a market valuation of $21 billion, are discussing.

TOMS Capital Investment Management tends to work behind the scenes on activist campaigns and has previously been involved in pushing for changes at Colgate-Palmolive.

Kellanova ( K ), which makes Pop-Tarts, reported quarterly earnings on Thursday, beating Wall Street estimates for first-quarter sales and profit on higher prices and firm demand for its breakfast cereals and ready-to-eat snacks.

Its stock price jumped roughly 9% in early trading and is exchanging hands at $61.29.

A representative for Kellanova ( K ) was not immediately available for comment and a representative for TOMS Capital Investment Management declined to comment.