Federal prosecutors have launched an investigation into the arrest of New York City Comptroller and mayoral candidate Brad Lander, who was briefly detained during an immigration court hearing on Tuesday.

Lander was taken into custody by federal agents after attempting to accompany an individual out of a courtroom at 26 Federal Plaza. That individual was also detained.

The comptroller was released about four hours later, emerging from the courthouse alongside Governor Kathy Hochul, who announced that the charges against him had been dropped.

“The arrest should never have happened,” Hochul said. “Brad Lander was standing up for due process and human dignity.”

The U.S. Attorney’s Office is still reviewing the incident and has not ruled out future charges, pending the results of its investigation.

Meanwhile, Representatives Jerrold Nadler and Dan Goldman are expected to visit Federal Plaza on Wednesday to conduct oversight into the incident and broader immigration enforcement practices.