(RNN) - Chipotle announced Tuesday that it found unauthorized activity on a network that supports its payment system. The company has enlisted cyber security firms and law enforcement to help with an investigation.
The hack affected the company's credit card system from March 24 through April 18, Chipotle CEO Jack Hartung said. The company did not disclose the number of restaurants that were hacked or which customers may have been affected.
"We believe the actions taken have stopped the unauthorized activity," Hartung said during the company's earnings call on Tuesday. The Denver-based company reported strong first-quarter earnings, but after news of the hack, the burrito chain's stock price fell below $480, reports Restaurant News.
A 17.8 percent same-store sales growth in the first quarter of 2017 marked the first time that Chipotle's stock price rose above February 2016, after the chain was plagued with an e coli breakout.