The FBI has begun investigating after a slew of fake texts appeared from an imposter claiming to be Vice President Mike Pence’s top aide, according to news reports.

The Wall Street Journal, which broke the news Friday, said the messages were received by a handful of Republican members of Congress from someone impersonating Alyssa Farah, Pence’s press secretary who once served as a House staffer.

After becoming aware of the texts, Rep. Liz Cheney (R-Wyo.) brought the matter to the attention of the House Sergeant at Arms office, the Journal reported.

Rep. Adam Kinzinger’s (R-Ill.) spokeswoman Maura Gillespie told CNN and The New York Post that he received the messages at various times, and reported them to authorities. Gillespie added that “only recently has there been a renewed interest to address the issue” despite hoaxes of this nature occurring for months.

While the messages targeted multiple people, “at least one member has been repeatedly engaging with the imposter,” the Journal reported.

A White House official confirmed to the outlet that the texts have been deemed a potential security threat, and the phone number from which they were sent has now been blocked.