A number of inverse VIX ETFs stopped trading on Tuesday, including the Horizons S&P 500 VIX Short-Term Futures Daily Inverse ETF (HVI), which trades on the TSX.

Horizons said that it halted trading of HVI after the “extreme volatility” in the VIX futures market in after-hours trading Monday. An IIROC release said trading halted at 8:52 a.m. It began trading again at 1:15 p.m. but was again halted, according to IIROC releases.

The Cboe Volatility index (VIX) measures market volatility and is often referred to as the “fear index.”

“The unexpected level of volatility has impaired the trading of the underlying derivatives used by many VIX-related exchange traded products that seek to provide inverse exposure to the S&P 500 VIX Short-Term Futures,” a Horizons release said. It also temporarily suspended redemptions and new subscriptions for the ETF.

Three U.S.-listed inverse VIX ETFs—VelocityShares Inverse VIX Short-Term ETN, ProShares Short VIX Short-Term Futures ETF and VelocityShares Daily Inverse VIX Medium-Term ETN—were also halted, Reuters reported Tuesday. The three ETFs also had a short sell restriction placed on them, the report said.

Credit Suisse announced trading of the VelocityShares Inverse VIX Short-Term ETN would end on Feb. 20, CNBC reported.

Horizons’ HVI “seeks daily investment results, before fees, expenses, distributions, brokerage commissions and other transaction costs that endeavour to correspond to the inverse (opposite) of the daily performance of the S&P 500 VIX Short-Term Futures Index.”

In addition to that ETF, Horizons also announced that it would not be accepting new subscriptions for units of the BetaPro S&P 500 VIX Short-Term Futures™ 2X Daily Bull ETF( HVU), which also trades on the TSX. IIROC halted trading on HVU at 9:10 a.m. It resumed trading but was again halted on Tuesday afternoon.