Various members of the US Congress want to gain more insight through hearings about the special price development of a number of shares on the stock exchange, including GameStop and cinema chain AMC.

In recent days, small investors have been gathering via social media to sharply boost the stock market value of more or less written-off companies, at the expense of large hedge funds, which saw billions of dollars evaporate.

Via the WallStreetBets page on the Reddit forum, private investors are calling on each other to massively buy shares of companies that have to contend with so-called short sellers, or investors who speculate and hope for a price drop.

As a result, the value of video game retailer GameStop increased by 1,000 percent in one week.

According to the chairman of the financial sector committee in the House of Representatives, Maxine Waters, more explanation is needed about recent developments.

She also points out the alleged evil role of hedge funds, investment firms that take more risk with complex trading strategies to maximize profit.

"We need to tackle hedge funds whose unethical behavior caused the recent swings and we need to examine the markets in general," said Democrat Waters.

She added that the role of online investment apps should be explored, in addition to the fact that investing is increasingly presented as a game to individuals.

Senate Banking Committee Chair Sherrod Brown also announced a hearing on the recent craze in US stock markets.

"People on Wall Street only care about the rules if they are the ones in pain. American workers have known for years that the system on Wall Street is broken because they pay the price," said Brown.

See also: For example, small investors at the expense of hedge funds become rich with GameStop

Criticism of investment app Robinhood

Democrats and Republicans have fiercely criticized the popular investment app Robinhood.

He decided that his customers could no longer buy shares of GameStop and certain other companies after the stormy price trend of the past few days.

New York State Attorney Letitia James announced that he was investigating the matter.

Via Twitter, Robinhood founder Vlad Tenev defended the decision by pointing out the capital requirements that the app must meet as a broker for stock trading.

Allowing the massive buyback of GameStop shares to proceed undisturbed would involve too great a risk.

"Some of the financial requirements fluctuate based on the price movements in the market, and they can be substantial in the current circumstances," Tenev wrote.

"These requirements are there to protect investors and markets, and we take our obligations very seriously."