Trading volume for Intelligent Systems Corp. returned to normal levels Thursday on the New York Stock Exchange after a 418 percent spike the day before.

The NYSE on Wednesday wanted to know why there was a sudden explosion of trading in the Norcross company that normally sees a fraction of the activity.

Intelligent Systems Corp., however, indicated it was also puzzled at the activity, which saw trading volume rise 418 percent. According to market data, Intelligent Systems’ 90-day average daily volume of 12,688 reached 65,703 shares on Wednesday.

On Thursday, trading volume was 10,861. After dropping to $1.60 around 11 a.m. from its Wednesday close of $1.69, a decline of about 5 percent, the stock recovered, closing at $1.67, down 1 percent.

Chief Financial Officer Bonnie Herron told The Atlanta Journal-Constitution on Thursday the company still had no explanation for Wednesday’s activity.

Intelligent Systems invests in information technology and industrial products companies. Its main subsidiaries are ChemFree Corp., a provider of washing systems used to clean parts, and CoreCard Software, which provides services to credit processors.

In a release about Wednesday’s trading activity, the company said its policy is not to comment on market activity or rumors. “However, the company did confirm to the NYSE that it is not aware of any material corporate developments beyond its most recently issued news releases,” it said in a statement.

The company recently reported increases in both revenue and net income for the third quarter. While it warned of an expected decline in revenue from leased equipment at ChemFree, Intelligent Systems said domestic sales were strong at the subsidiary. The company also reported growth in software license and services revenue for CoreCard.

In addition to the sharp rise in trading volume, the company’s shares also saw swings Wednesday. The stock, which closed at $1.79 on Tuesday, reached an intra-day high of $1.84, up 3 percent, and a low of $1.61, down 10 percent, before closing at $1.69, down nearly 6 percent.