Video game retailer GameStop, whose market volatility earlier this year led the so-called “meme stocks” craze, disclosed it is cooperating with an investigation launched by the Securities and Exchange Commission (SEC).

During a two-week span in late January and early February, GameStop’s value jumped from $2 billion to over $24 billion as a rush of small investors bought the stock, egged on by others on social media. The stock subsequently crashed, in part because of a brief trading halt by FinTech platform Robinhood. Similar wild swings of value occurred with other previously moribund stocks like AMC Entertainment Holdings and BlackBerry.

“On May 26, 2021, we received a request from the Staff of the SEC for the voluntary production of documents and information concerning a SEC investigation into the trading activity in our securities and the securities of other companies,” GameStop wrote in a regulatory filing Wednesday. “We are in the process of reviewing the request and producing the requested documents and intend to cooperate fully with the SEC Staff regarding this matter. This inquiry is not expected to adversely impact us.”

“Other companies” might include AMC, BlackBerry, Nokia, and more whose stock values have been pushed by similar buying and selling patterns fueled on social media.

Compliance professionals predicted early that the SEC would examine the meme stocks craze for potential market manipulation as a “pump-and-dump” scheme.

But new SEC Chair Gary Gensler said at the Global Exchange and FinTech Conference on Wednesday that he asked staff to widen the agency’s lens even more to examine some of the forces and patterns in the market that contributed to the frenzy.

“I’ve asked staff to make recommendations for the Commission’s consideration on best execution, Regulation NMS, payment for order flow (both on-exchange and off-exchange), minimum pricing increments, and the NBBO (national best bid and offer), with the aim of continuing to make our markets as efficient as possible,” he said.

Gensler pointed out 47 percent of shares sold are not done on the open public exchange but instead by wholesalers (38 percent) and alternative trading systems (9 percent). Many of the retail investor trades executed in meme stocks took place via these less-public exchanges.

Robinhood drew criticism after halting trading for two days when GameStop’s stock hit its peak. The platform said it had to stop trading because it did not have enough money to meet collateral requirements.

Gensler’s criticism of Robinhood’s business model didn’t focus on the trade stoppage, however. He said Robinhood’s model of using payment for order flow—in which Robinhood earns money not from its customers but from the wholesaler brokers that execute trades on behalf of Robinhood’s customers—is a problem. Thinking they are getting a bargain when they receive zero commission trades, Robinhood’s customers may be disadvantaged, Gensler said, because they are not getting the best available stock price when buying or selling through Robinhood.

“Robinhood explicitly offered to accept less price improvement for its customers in exchange for receiving higher payment for order flow for itself,” he said. “As a result, many Robinhood customers shouldered the costs of inferior executions; these costs might have exceeded any savings they might have thought they’d gotten from zero commission trading.”

Gensler also said he favors reducing the time required for trades to be executed, from the current two days (T+2) to one day or even same day.