Investors pounced on Shake Shack stock in after-hours trading Thursday after the fast-casual eatery beat sales and earnings-per-share estimates for the three months ending March 30.

The small but popular New York City-based burger and frozen custard chain said sales at stores open at least two years jumped 9.9 percent in the quarter over the same period last year. It also raised its revenue forecast for 2016 to between $245 million and $249 million from a previous estimate of $237 million to $242 million.

The company expects same-store sales (an important retail metric that excludes recently opened stores) to rise between 4 percent and 5 percent and expects to open 16 more outlets this year instead of the previously stated 13.

 “With the extraordinary results in Q1, we are off to a strong start to the year,” CEO Randy Garutti said in the earnings statement.

Sales touched $54.2 million in the quarter, up from $37.8 million in the year-ago period. A Thomson Reuters poll of analysts had on average expected sales to ring in at $52.1 million. Adjusted earnings per share increased to 7 cents from a loss of $1.06 in the same period last year. Analysts had expected a gain of 6 cents per share.

The restaurant chain was founded in 2000 by restaurateur Danny Meyer as a food kiosk in New York City’s regal Madison Square Park and has grown to 86 directly owned and licensed outlets in the U.S. and globally. It opened three U.S. outlets (two in Arizona and one in West Hollywood, California ) and a licensed franchise store in Muscat, Oman, in the first quarter.

Shake Shack stock gained nearly 6 percent in after-hours trading, to $34.42. Shares are down 13 percent for the year and 49 percent over the past 12 months.