In this file photo, a pair of Bank of America-Merrill Lynch specialists work at their post on the floor of the New York Stock Exchange. AP
Shares of GameStop surged anew following the open after another social media post associated with influential investor Keith Gill.
About 15 minutes into trading, the Dow Jones Industrial Average was flat at 38,677.29.
The broad-based S&P 500 gained 0.4 percent to 5,298.56, while the tech-rich Nasdaq Composite Index advanced 0.9 percent to 16,888.10.
US stocks have been choppy in recent weeks amid shifting sentiment on the likelihood of Federal Reserve interest rate cuts this year.
The ECB is expected to begin cutting eurozone interest rates from historic highs this week, but sticky inflation means the move is unlikely to kickstart a rapid easing cycle.
Among individual companies, GameStop jumped more than 40 percent after a Reddit account associated with Gill posted a portfolio that implied that he had built a sizable position in the company.
Waste Management dropped 1.7 percent after announcing a plan to acquire Stericycle, which specializes in medical waste services, for $7.2 billion. Stericyle surged 15 percent.
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