Tom Homan, who was later named President Trump’s border czar, was recorded in September 2024 accepting a bag with $50,000 in cash in an undercover F.B.I. investigation, according to people familiar with the case, which was later shut down by Trump administration officials.

Mr. Homan’s encounter with the undercover agents, recorded on audiotape, led him to be investigated for potential bribery and other crimes, after he apparently took the money and agreed to help the agents — who were posing as businessmen — secure future government contracts related to border security, the people said.