Ackman feels like Mexican, buys 10 pct of Chipotle

Chipotle shares, under siege after a series of food scares erupted just over a year ago, are surging before the opening bell after activist investor Bill Ackman revealed that he's become the taco chain's second largest investor.

Ackman's Pershing Square Capital Management LP has a 9.9 percent stake in Chipotle Mexican Grill Inc., according to a filing with the Securities and Exchange Commission.

Shares jumped more than 6 percent in premarket trading Tuesday.

Ackman has in the past shaken up the leadership of ailing companies, and that is what Chipotle has become since the first outbreak of E. coli in July last year.

Shares that hit an all-time high close to $760 around that time, have been cut in half.

Chipotle did not immediately respond to a request for comment.