The FBI is investigating the use of high frequency trading, following on from a multi-year crackdown on insider trading, which has amassed 79 convictions of hedge-fund traders and others.
Agents are looking at whether high-frequency trading (HFT) firms break US laws by acting on private information in order to gain an edge over their competitors.
"Trading ahead of other investors based on information about orders that other investors can't see could violate insider-trading laws," said an FBI spokesperson in a media statement.
There are growing concerns that the use of HFT distorts the market as it rapidly raises and lowers prices in an attempt to make a super-fast profit.
Eric Schneiderman, New York Attorney General, was one of the first to open a broad investigation as to whether US stock exchanges give high frequency traders an improper advantage.
HFT is a service that is available to everyone and firms, such as Nasdaq OMX Group and IntercontinentalExchange Group for example, pay thousands of dollars a month for it.
The news couldn't have come at a more relevant time following on from yesterday's release of Michael Lewis' book, Flash Boy: A Wall Street Revolt, which highly criticises the use of HFT and alleges that Wall Street is rigged to benefit the players who use this tactic.
The practice of HFT originally came into the public eye during the 2010 Flash Crash when a mutual fund firm were selling an unusually high volume of E-Mini S&P contracts which was a larger amount than the available number of buyers.
High frequency traders then started selling aggressively, accelerating the price decline. This lead to an average reduction of 9% on stocks.
Regulators have been focusing on the use of HFT for some time, but allegations are now shifting towards whether it is deemed unfair, and even possible criminal activity which could include wire fraud, securities fraud and insider trading.
Daniel Hawke, the head of the Securities and Exchange Commission's market-abuse unit, said in 2012 that the agency was examining practices such as co-location and rebates that exchanges pay to increase transactions.