Last week's wild market swings have drawn the attention of one of Wall Street's main regulators, which is looking into whether options prices linked to the widely followed Cboe Volatility index were manipulated.

The Financial Industry Regulatory Authority is looking at S&P 500 options trading activity to see whether traders placed orders to influence prices, The Wall Street Journal reported Tuesday. FINRA would not comment on the report.

It isn't a stretch to imagine that regulators are examining the violent swings in the stock market last week that accompanied a spike in volatility. The VIX, as the index is better known, is calculated based on the price of options and was designed to be a barometer of traders' concerns about the near-term direction of the market.

For most of last year, the VIX traded in record low territory, but it spiked last week as the S&P 500 had a sharp sell-off. That sent shock waves through the markets and wiped out a Credit Suisse exchange-traded product linked to the VIX. On Monday, a person who would not identify himself, sent a letter to the SEC saying the VIX is subject to manipulation.

The Cboe, which derives an estimated 25 percent of its revenue from VIX-related products and trading activity, has tried to put a positive spin on events, saying its markets were orderly and functioning. But its shares sold off more than 15 percent last week. They are up 4 percent in Tuesday afternoon trading.