The video game retailer GameStop’s stock saw more extreme volatility Thursday after the popular trading app Robinhood restricted transactions for it and other hot stocks whose values were boosted by a mob of online traders.

In a day of wild trading, GameStop’s stock opened at $350, shot to $469, plunged to $115, then climbed and fell several times to rest at just over $230 by early afternoon.

On Thursday morning, Robinhood — which says it has more than 13 million users — announced that “in light of recent volatility,” the stock and several others would be restricted, only allowing traders to close their positions, which would allow them to sell but not buy more shares.

Jan. 28, 202103:57

“We’re humbled to have helped many people invest in the markets for the first time,” the company said in a statement released on its blog. “And we’re determined to provide new and experienced investors with the tools and resources to help them invest responsibly for their long-term financial futures.”

However, furious users complained online that they were unable to transfer funds to their bank account or to other trading platforms that had not restricted the stocks. Robinhood did not immediately respond to a request for comment.

The stocks included AMC, BlackBerry, Bed Bath & Beyond, Express, GameStop, Koss, Naked Brand Group and Nokia. Traders will only be able to close their positions, the company said.

Other online exchanges, AmeriTrade, Interactive Brokers, and Webull also said they were restricting trades of the hot stocks. Brokerage Charles Schwab said it was increasing margin requirements.

“Closing out a position could involve buying or selling,” Greg McBride, chief financial analyst for Bankrate, told NBC News in an email. “Someone currently holding the stock would sell it to close out their position. Someone shorting the stock can buy the stock back — to replace the borrowed shares that were sold short — to close out the position.”

Robinhood also announced it was increasing the amount of money traders would need to put down for certain securities bought on margin.

Some of the amateur traders had made their purchases on margin, which allows them to pay only a percentage of the stock’s worth and borrow the rest from the broker. If the stock goes up, they profit by reaping much more than they put in — but if it goes down, they’re forced to repay more than they put in, magnifying their losses.

Investors buying on margin precipitated the Black Tuesday Wall Street crash before the Great Depression. When prices fell and people were forced to repay their loan, they were wiped out.

The previously underperforming stocks first got a boost in a trading forum on the popular online link-sharing site Reddit after its members said they wanted to rebel against Wall Street hedge funds that had shorted a number of stocks. By egging one another on to buy up the stocks, the price rose, forcing some of the funds to buy more stocks to cover their positions, driving the stock higher. One fund was forced to take a multibillion-dollar investment to cover its exposure, to the delight of the online crowd.

Binh Nguyen, 29, a nail technician from Louisville, Kentucky, said he discovered Robinhood day trading as a way to make rent for him and his elderly mother after losing income due to pandemic downturns. “The government keeps saying they’re sending help, but we don’t see anything,” he said.

He said he had a “panic attack” Thursday morning when he saw GameStop stock “crashing” and he could not execute the trades he wanted on Robinhood.

“I saw the Nasdaq CEO saying maybe they should halt the market so investors can reposition themselves,” Nguyen said by phone. “They’re thinking about their half. What about me and my next-door neighbor, how come we don’t get a chance to reposition ourselves?”

Other Robinhood users said they were happy to jump on the trade as it took off and hoped they could get out before it’s over, no matter how it got started or amplified.

“I know this is a bubble and it’s going to pop. I know a lot of it is bots,” and other inauthentic manipulation, Justin Reidy, 22, a software developer from Missouri, said by phone. He invested more than $5,000 in several of the stocks popular on the Reddit forums, including GameStop.

“Those online communities — I don’t think they’re treating it any differently than hedge funds treating it like a casino.”

Reidy and others see themselves as part of an online movement to put more control over the market and companies into the hands of individual traders who can invest in companies not simply based on price-to-earnings ratios and other fundamentals, but in companies they believe in.

“For a decade now, retail investors have been the victims of short side manipulation by hedge funds via social media,” Joshua Mitts, a professor at Columbia Law School who studies market manipulation, said by phone. “The Securities and Exchange Commission has no policy rulemaking on social media and trading,” he said. “The SEC should have data scientists sitting with every enforcement lawyer to very quickly in real time identify actors who may be doing shady things, and immediately intervene to stop bubbles like this from happening.”

The SEC on Wednesday said it was “actively monitoring” the amplified market behavior.

Online traders railed against the restrictions by Robinhood, but experts say it’s in their best interest.

“It helps protect people from themselves — those who are late to the party and will get stuck holding the bag when this mania comes to a likely sudden and inglorious end,” McBride, of Bankrate, said.

Some of the online traders on Reddit have already moved on to another craze: silver. They’re buying up silver miners and exchange-traded funds, and the price of the metal itself is shooting up, boosted by claims banks were manipulating gold and silver prices.

Mitts also warned that what on the one hand could look like an authentic online movement of ideologically driven investors and follow-on traders capitalizing on the growth could have been started by a small group of actors trying to manipulate the market.

“It could be a hedge fund, it could be an individual who is really sophisticated who knows how to buy in such a way to trigger behavior in the market, it could be a group in Macedonia,” he said.

“You could have at the core of this a few predatory hedge funds who are expert at the long side, buying early and selling at the top. We call that a pump and dump,” Mitts said. “We would be talking about destroying the savings of hundreds of thousands of people who bought in.”

The furor took on a heightened edge Thursday as online users circulated the address of Robinhood’s headquarters and called for a “peaceful protest.” Rep. Alexandria Ocasio-Cortez, D-N.Y., tweeted that the halting of trading was “unacceptable,” and Sen. Ted Cruz, R-Texas, tweeted “fully agree,” in reply.

One of the chief beneficiaries of the activity has been Ryan Cohen, co-founder and former CEO of online pet product giant Chewy — and, as of two weeks ago, a GameStop board member. Also GameStop’s largest shareholder, his 13 percent stake in GameStop shares netted him around $2 billion at one point — for an initial investment of just over $75 million.