More congressional Democrats are urging the Justice Department’s Office of the Inspector General to look into Labor Secretary Alexander Acosta’s involvement in a 2007 plea deal with a hedge fund manager accused of abusing underage girls.

A group of 16 Senate Democrats Dec. 6 sent a letter to the DOJ’s office to review the case. The request comes days after a group of nearly 100 House members Nov. 30 urged a similar investigation.

The growing calls for a probe follow a Nov. 28 story by The Miami Herald detailing the plea agreement that Secretary Alexander Acosta, then a U.S....