The FBI has issued a warning about scammers impersonating FBI representatives to steal personal and financial information from victims by threatening them with fines or jail time. People have reported that they’ve been asked to immediately provide information to these scammers under the guise of helping an ongoing investigation or to clear themselves as a suspect. In situations like this the FBI advises everyone to reach out to their local field office to verify the identity anyone claiming to work for the FBI. Furthermore, the FBI will never request money from you to help with an investigation or for any other reason! If you run into this scam, or any other type of scam and fraud, please report it to the FBI Internet Crime Complaint Center (IC3) at www.IC3.gov.

Source - Scammers posing as FBI agents threaten targets with jail time