(Updated with analyst commentary.)

CHICAGO (TheStreet) -- Morton's Restaurant Group (MRT) shares spiked on Monday.

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Morton's shares jumped 12.2% to trade at $5.72. Nearly 135,000 shares were in play with 90 minutes left in the day's session, compared with their average daily trading volume of just 35,000.

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A lack of company-related news or regulatory filings suggest Morton's stock price gain may be the result of a small number of institutional buyers picking up a chunk of its shares. With a market cap of just over $93 million and share price around $5, it doesn't take much activity to move Morton's stock.

About a third of all Morton's shares are owned by private equity firm Castle Harlan, so there aren't that many MRT shares out there to buy and sell, Raymond James analyst Bryan C. Elliott told TheStreet, meaning it would only take one or two small institutional buyers -- or sellers -- to move the needle.

The analyst also said that restaurant stocks have been very strong in the past month or so on evidence of improving -- though still far from robust -- sales in the industry.

High-end steakhouses like Morton's have been reporting financial results well-above recent industry sales gains so far this year, Elliott said, so "the path of least resistance is up."

In a report over the summer, TheStreet tapped Morton's among the riskiest restaurant stocks for investors.

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The operator of Morton's The Steakhouse, Trevi and Bertolini's Authentic Trattorias restaurant chains missed analysts' consensus call with a quarterly net loss of $663,000, or 3 cents per share, in its most recently reported quarter. The bottom-line numbers did manage to improve dramatically from year-earlier losses of $6.5 million, or 41 cents per share.

The return of business travel -- and with it, corporate expense cards -- has led a slow-but-upward-trending rebound for Morton's. The Chicago-based restaurateur generates about 80% of its revenue from corporate card transactions.

Same-store sales, or sales at restaurants open at least one year, grew 7.1% in the second quarter, beating expectations, and comps were up 3% in July.

Morton's closed more underperforming restaurants than rival Ruth's Hospitality Group's ( RUTH - Get Report) Ruth's Chris as restaurant sales plummeted during the recession, and its sales figures outpaced in kind.

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A number of other restaurant stocks also traded higher Monday, though none by as strong percentages as Morton's.

Shares of BJ's Restaurants ( NJRI) added 3.5% after the small-cap restaurateur beat earnings expectations when it reported results last week.

The bar and grill chain said late Thursday its third-quarter profits surged more than 70%, and revenue jumped 24%, as comps increased 6.7%.

BJ's results led Sterne Agee analyst Lynne Collier to reiterate a buy rating on BJ's stock, citing the company's "impressive" quarterly results. She raised her earnings expectations for 2010 and 2011, and upped her price target on the stock to $33.

Industry darling Chipotle Mexican Grill ( CMG - Get Report), along with Cheesecake Factory ( CAKE - Get Report) and fast-food behemoth McDonald's ( MCD - Get Report) all reported stronger-than-expected quarterly results last week as well.

>> Chipotle, Cheesecake Factory, BJ's Beat Expectations

Morton's is due to report third-quarter results on Nov. 1. Analysts' consensus call is for Morton's to post a quarterly loss of $2.2 million, or 13 cents per share, on revenue of $67.2 million. In the year-earlier quarter Morton's posted a loss of $3.3 million on revenue of $65.1 million.

-- Written by Miriam Marcus Reimer in New York.

>To follow the writer on Twitter, go to @miriamsmarket.

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