Dallas police and firefighters are withdrawing hundreds of millions from their retirement plan following a series of investment blunders, heightening the risk that a major U.S. pension fund could run out of money.

Officers say they are pulling their retirement savings because of concerns about the fund’s finances. A series of aggressive real-estate bets from Hawaii to Paris and a conflict over the value of those properties triggered more than $500 million in losses, leaving the fund with enough to pay just 45% of future benefits. Officials are warning the pension could go broke by 2027.