Deephaven Capital Management has suspended withdrawals a pair of hedge funds after investors sought to redeem huge portions of them.

The Minnetonka, Minn.-based hedge fund arm of Knight Capital Group has frozen its $1.6 billion Global Multistrategy Fund and $70 million International Volatility Strategies Fund, Bloomberg News reports. Investors had made redemption requests totaling about 30% in the multistrategy fund, and about 60% of the volatility fund.

“This level of redemptions in the current market environment forces the question of whether such redemptions can be processed in the ordinary course without disadvantaging both continuing and later redeeming investors,” Deephaven CEO Colin Smith told investors in a letter. Smith added that the firm’s prime brokers had upped their margin requirements, forcing it to sell assets to meet margin calls. He said the firm was working on creating a schedule for redemptions.

The multistrategy fund is down approximately 25% this year, as it has fallen by about 10% this month.

In January, Deephaven shuttered its $780 million event-driven fund after investors tried to redeem some two-thirds of its assets.