Updated to include CEO comments from earnings call.

Investors are still yearning for more meat on the bone with respect to Shake Shack's (SHAK) - Get Report outlook for 2016.

Shares of the better burger joint plunged by more than 9% in morning trading on Tuesday as the company reported its fourth-quarter earnings after the close on Monday and reiterated its previous cautious full year same-store sales guidance. The company anticipates its same-store sales rising 2.5% to 3.0% this year.  

In the third quarter, Shake Shack had delivered a strong 17.1% gain in same-store sales and boosted its 2015 same-store sales growth target back in November to 11% to 12% from a high-single digit percentage. Yet, it also offered up a tepid initial outlook for 2016 that would have represented a marked slowdown in growth from the prior year.

Shake Shack will open a new spot in New York City's Herald Square later this year.

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On Monday, the company re-affirmed that guidance, despite a what looks like a promising start to the year and the sales lift from a new fried chicken sandwich, which debuted at all locations Jan. 14. 

Same-store sales surged 11%, ahead of Wall Street estimates for a 7.3% increase. Earnings adjusted for one-time items were 8 cents a share compared to forecasts of 7 cents a share. For 2015, Shake Shack's same-store sales gained an impressive 13.3%, above the high-end of management's guidance.

"We have had a great start to the quarter," said Shake Shack CEO Randy Garutti on a call with analysts, adding the chicken sandwich is a top-five seller on the menu on average.

According to execs, though, Shake Shack's less-than-juicy outlook stems from the fact they will be encountering tough sales comparisons to the prior year beginning in the second quarter. "It's too early to update guidance," said Shack's CFO Jeff Uttz.   

Shake Shack will launch an undisclosed new limited-time burger in the second half of 2016.

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Meantime, Shake Shack has not been hurt by the fast food promotional wars that kicked off between McDonald's (MCD) - Get Report , Yum! Brands (YUM) - Get Report owned Pizza Hut and Restaurant Brands International's (QSR) - Get Report Burger King in January. 

Said Garutti, "We have not seen an impact from the discounts in the fast food industry -- and we have no intention of entering that game."