A top administration official to the governor of New Jersey, Philip D. Murphy, resigned abruptly last week with no public explanation. This week news reports emerged that the aide, Albert J. Alvarez, had been the subject late last year of a sexual assault investigation by a county prosecutor.

Now Mr. Alvarez’s departure and the circumstances surrounding it are roiling Trenton, with top Republicans in the Legislature calling for hearings and Democrats working behind the scenes to find out more about the investigation and the actions taken by the Murphy administration.

At an unrelated event on Tuesday, Mr. Murphy, a Democrat who was elected in November, declined to offer any details about Mr. Alvarez’s resignation.

“I know that Al has resigned and beyond that I have no more color to offer,” Mr. Murphy told reporters.