(Reuters) - BlackRock Inc, the world’s largest asset manager, warned of the risk of so-called inverse Exchange-Traded Products (ETPs) following Monday’s steep decline in financial instruments that bet against wild downward swings in the markets.

FILE PHOTO: The BlackRock logo is seen outside of its offices in New York City, U.S., October 17, 2016. REUTERS/Brendan McDermid/File Photo

Monday’s stock market rout left two of the most popular ETPs, which investors use to benefit from calm rather than volatile conditions, facing potential liquidation, market participants said.

The VelocityShares Daily Inverse VIX Short-Term ETN sank 84 percent in after-hours trading, while the ProShares Short VIX Short-Term Futures ETF fell nearly 79 percent as investors questioned if they could survive the volatility shock.

The products seek to provide inverse exposure to VIX short-term futures and, when that measure spikes, the investment loses value, at which time ETP issuers could liquidate the shares.

It was not immediately clear if the issuers would opt to liquidate these products.

BlackRock did not mention the products by name, but reiterated its long-held view that inverse and “leveraged” ETPs that double or triple market returns “are not ETFs, and they don’t perform like ETFs under stress,” adding “that’s why iShares does not offer them.”

IShares is the brand name for BlackRock’s exchange-traded funds (ETFs).

BlackRock also called for a regulatory classification system to label levered and inverse ETPs differently than plain-vanilla ETFs, to show the risks associated with such products.

SVXY sponsor ProShare Capital Management LLC declined to comment. Janus Henderson Group plc, which markets the VelocityShares notes, could not be reached immediately.

Credit Suisse Group AG, which issued the VelocityShares notes, traded down 6 percent after-hours.

“The XIV ETN activity is reflective of today’s market volatility. There is no material impact to Credit Suisse,” said spokeswoman Nicole Sharp. She declined to comment further.

Stocks plummeted in highly volatile trading on Monday, with the benchmark S&P 500 index and the Dow Jones Industrials suffering their biggest respective percentage drops since August 2011 as a long-awaited pullback from record highs deepened.

For the Dow, the fall at one point of nearly 1,600 points was the biggest intraday point loss in Wall Street history.