Knight's share of volume in the Nasdaq 100 tracking ETF was 20 percent at noon Tuesday, according to Thomson Reuters AutEx data, above its usual average of 13.3 percent.

In other heavily traded stocks, Knight was handling more volume than in the last few days, but volumes had not reached the levels from before the snafu, according to those figures.

As a market maker, it provides liquidity to equity markets by stepping in to buy and sell stocks, using its own capital to ensure orderly activity.

Knight shares opened trading more than 6 percent higher but gave up all the gains during the course of the day. The stock closed down 1 cent at $3.06, giving Knight market capitalization of $301.5 million, slightly below the bailout amount under the deal with a consortium led by Jefferies Group Inc. Under the deal, the consortium will have three seats on an expanded board.