Investigators with the Department of Homeland Security made an unannounced visit on Wednesday to the home of a former Immigration and Customs Enforcement spokesman who abruptly resigned three months ago because he could not bring himself to lie on behalf of the Trump administration.

The former spokesman, James Schwab, announced his resignation from the agency on March 12. He said he quit because he did not want “to perpetuate misleading facts” during a dispute between the Justice Department and the mayor of Oakland, Calif. Mr. Schwab had stayed quiet since then, until he sat down on Wednesday for an interview with a CBS News reporter at his California home.

But two men in dark suits interrupted the interview, which aired on Thursday morning, knocking on Mr. Schwab’s front door. They said they worked in the Department of Homeland Security’s Inspector General’s office and wanted to speak with Mr. Schwab.