New York's attorney general is now investigating the stock trading app Robinhood after it restricted trading on certain stocks after GameStop and others saw massive spikes this week.

GameStop stock has rocketed from below $20 earlier this month to close around $350 Wednesday as a volunteer army of investors on social media challenged big institutions who had placed market bets that the stock would fall. The action was even wilder Thursday: The stock swung between $112 and $483 before closing down 43.2% at $197.44.

Robinhood said Thursday that investors would only be able to sell their positions and not open new ones in some cases. Robinhood also required investors to put up more of their own money for certain trades instead of using borrowed funds.

Assemblyman Ken Zebrowski is calling for an investigation as well into Robinhood's decision. He says he wants the state attorney general to see if Robinhood could've made this move to support big institutional investors in the market at the expense of people making trades for their portfolios or retirement accounts.

"It's important that the stock market be fair and accessible to everybody. So when you see a situation where you may have major institutional players that invest billions of dollars seem to get a leg up on ordinary folks, it's important that we investigate that and get to the bottom of it and change the rules if necessary," says Zebrowski.

Zebrowski says he doesn't have evidence of any wrongdoing by Robinhood. He does say though, that the news of trades being stopped led to many angry calls from constituents.

The state Attorney General Letitia James released a short statement, simply acknowledging the concerns and pledging to investigate.

The Associated Press contributed to this report.