DENVER -- Chipotle is alerting the public about a data breach which may have allowed crooks to get access to the payment information of thousands of customers.The company said it identified unauthorized activity on the network that supports payment processing.The investigation is focused on card transactions from March 24 - April 18, 2017.If you used your card at a Chipotle location during those dates you should closely monitor your bank statement and immediately notify the bank that issued the card about any questionable charges.Chipotle announced Tuesday a key sales figure rose more than expected in the first quarter as it works to recover from a series of food scares that had sent customers fleeing.The Denver-based chain said sales rose 17.8 percent in the first three months of the year, following a 29.7 percent decline in the year-ago quarter. Sales at stores open at least 13 months had turned positive in December after dropping steeply starting in late 2015.For the quarter, Chipotle earned $46.1 million, or $1.60 per share. Analysts had expected $1.29 per share, according to FactSet. Total revenue was $1.07 billion, topping the $1.05 billion analysts expected.Chipotle shares rose 5 percent in after-hours trading.