Beyond Meat Inc.'s shares tumbled on Monday on plans for another stock offering just three months after its IPO while demand for its plant-based burgers and sausages prompted an increase in its full-year sales forecast.

Trading was volatile and shares fell by more than 12 percent after hours on news of a 3.25-million share offering that includes 3 million shares from selling stockholders.

Proceeds are earmarked to raise funds to expand its manufacturing facilities that are being stretched by booming demand for its meat alternatives. Executives on a call with analysts declined to comment on the offering.

Beyond Meat's shares have surged by over 780 percent since the IPO in May as the company's meat alternatives entered the menus of restaurants such as Carl's Jr. and on shelves of grocers including Kroger Co.

Plant-based meat alternatives have seen booming interest from consumers and restaurants, supporting startups like Beyond Meat and its competitor Impossible Foods, and even sparking interest from veteran meat companies such as Tyson Foods Inc. and Perdue Foods, which now offer meat protein products mixed with plants.

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"For another growth stock, the top-line beat and raises would be enough to see a post-market rally, but there are a lot of Beyond Meat investors out there looking for any excuse to sell a stock that has rocketed so much since its IPO," said Kamal Khan, analyst at financial markets platform Investing.com.

Beyond Meat products are now sold at more than 53,000 retailers and restaurants worldwide, with demand boosted by the grilling season underway, Beyond Meat's CEO Ethan Brown said on Monday.

At supermarket chain Morton Williams, which owns 16 locations across New York City, some customers are buying Beyond Meat burger patties and sausages by the case, according to Victor Colello, the chain's director of meat and fish.

"Beyond Meat is really flying off the shelves. My business with it has almost doubled and we're sold out at times," Colello said. The latest version of the burgers is made from peas, brown rice, sunflower seeds and mung beans.

Net revenue rose nearly four-fold to 67.3 million U.S. dollars in the three months ended June 29, above Wall Street's estimate of 52.71 million U.S. dollars, according to Refinitiv IBES data.

The company said it expects net revenue to rise over 170 percent to 240 million U.S. dollars in 2019, up from the prior 210 million U.S. dollars it had forecast just last month.

The El Segundo, California-based company reported a net loss of 9.4 million U.S. dollars, or a loss 24 cents per share, compared with a loss of 7.4 million U.S. dollars, or a loss of 1.22 U.S. dollars per share in the year-ago period.