Goldman Sachs (GS -0.2%), Barclays (BCS -1%), and Credit Suisse (CS -1.2%) are among the banks NY Attorney General Schneidermann has requested information from about their use of dark pools, reports Dow Jones.
Dark pools are systems set up by the banks to allow clients to trade large blocks of stock outside of the major exchanges.
Earlier this year, Goldman sent out checks to clients after discovering errors in trades in its Sigma X dark pool - the world's largest - from back in 2011. It was also reported that Goldman was considering selling Sigma X, a move management has denied.
Previously: Goldman considers shuttering dark pool