WASHINGTON (Reuters) - The U.S. securities regulator on Friday suspended trading in the securities of 15 companies because of “questionable trading and social media activity,” the latest in a string of temporary trading halts amid volatile trading in so-called “meme stocks.” The Securities and Exchange Commission acted because none of the companies have filed any information with the regulator for over a year, it said in a statement. This is the regulator’s third and largest wave of suspensions in response to social media activity. Retail interest in certain stocks, most notably GameStop Corp, has surged in a social media frenzy, leading to volatile trading. The SEC is continuing to review market and trading data to spot other securities to “to potential attempts to exploit investors during the recent market volatility,” the agency said on Friday. For a full list of the suspensions announced on Friday, go here: here.