Shares of Chipotle Mexican Grill Inc. rallied 6% late Tuesday after the fast-casual restaurant chain reported first-quarter earnings and sales above expectations thanks to improved customer traffic, fewer promotions, and higher average checks. Chipotle said it earned $46.1 million, or $1.60 a share, in the quarter, versus a loss of 88 cents a share in the year-ago period. Sales were up 28% to $1.07 billion. Analysts polled by FactSet had expected adjusted earnings of $1.29 a share on sales of $1.05 billion. Food costs were 34% of the company’s revenue, a decrease over the first quarter of 2016, thanks to lower food waste and testing costs, and bringing the preparation of lettuce and bell peppers back to the restaurants, Chipotle said. But the decrease was partially offset by higher avocado prices, it said.