AMC, other 'meme' stocks jump; regulator signals concern

By Aaron Saldanha, Sinéad Carew and David Randall

(Reuters) -Shares of AMC Entertainment Holdings Inc and other "meme stocks" jumped on Monday, extending a rally in social-media favorites into a third week as message boards hummed with talk of squeezing Wall Street short-sellers.

The sharp gains prompted the U.S. Securities and Exchange Commission to say it was looking into signs of market manipulation given the "volatility in certain stocks."

The volatility has challenged analysts, and two of them in the past week have stopped covering video game retailer GameStop, whose shares soared in January in a retail-driven rally.

Cinema operator AMC jumped almost 15%, putting its gain over the past five sessions at 111%. BlackBerry's U.S. listing surged 14% and is now up 57% since the start of June.