Standard Life Investments has frozen its U.K. property fund, saying the number of investors asking to withdraw money has increased following the EU referendum.

Citing “exceptional market circumstances,” the company SL., -4.50%  said the trading suspension took effect midday Monday for the $3.9 billion fund, which invests in commercial real estate in the U.K.

“The suspension was requested to protect the interests of all investors in the fund,” the company said in a news release.

A report from the BBC notes that Standard Life Investments wrote down the value of the fund by 5% last week and said the Brexit vote had hurt valuations for commercial properties. The company said in its latest release that it would ends the suspension as soon as it’s practical, and review the decision every 28 days, according to the BBC.