F.B.I. Director Kash Patel said on Friday that agents had arrested a county judge in Milwaukee on charges of obstructing immigration enforcement. A spokesman for the U.S. Marshals confirmed the arrest of a sitting judge, a major escalation in the Trump administration’s battle with local authorities over deportations.

The bureau arrested Judge Hannah Dugan on suspicion that she “intentionally misdirected federal agents away from” an immigrant being pursued by federal authorities, Mr. Patel wroteon social media. He later deleted the post for reasons that were not immediately clear. An F.B.I. spokesman did not immediately respond to a request for comment.

Brady McCarron, a spokesman for the U.S. Marshals, confirmed that the judge had been arrested by F.B.I. agents on Friday morning. The charging document against the judge was not immediately available in federal court records.

The Trump administration has vowed to investigate and prosecute local officials who do not assist federal immigration enforcement efforts, denouncing what they call “sanctuary cities” for not doing more to assist federal apprehensions and deportations of millions of undocumented immigrants.

The Milwaukee case involves a frequent flashpoint in that debate, when immigration agents try to arrest undocumented immigrants who are appearing in state court. Local authorities often chafe at such efforts, arguing they endanger public safety if people dealing with relatively minor legal issues feel it is unsafe to enter courthouses.

In the first Trump administration, a local Massachusetts judge was indicted by the Justice Department on charges of obstructing immigration authorities. The charges were dropped after the judge agreed to refer herself to potential judicial discipline.