The FBI last month requested an interview with the whistleblower whose complaint fueled the impeachment inquiry into President Donald Trump and Ukraine, a person familiar with the situation said Wednesday.

An agent from the FBI’s Washington field office reached out to the whistleblower’s lawyers last month to seek an interview about the substance of the complaint, according to this person, who insisted on anonymity to discuss the request with The Associated Press.

The person said it was clear from the FBI that the whistleblower was not regarded as the target of any investigation but rather a potential witness. It was not immediately clear what specifically the FBI might be looking into. The requested interview has not taken place.

An FBI spokeswoman declined to comment on the request, which was first reported by Yahoo News.

The whistleblower, a CIA officer, filed a complaint on Aug. 12 about Trump’s phone call weeks earlier with Ukraine’s president, Volodymyr Zelenskiy. During the call, Trump pressed for investigations into Democratic rival Joe Biden and into the 2016 U.S. presidential election.

A rough transcript of the call was released in September by the White House. The Democratic-controlled House has subsequently opened an impeachment inquiry centered on Trump’s effort to seek political investigations at the same time the U.S. was withholding hundreds of millions of dollars in military aid from Ukraine.

Trump has said he wants to know the identity of the whistleblower. House Democrats have said they do not need to hear from the whistleblower as part of the impeachment inquiry and have heard now from multiple witnesses who, unlike the whistleblower, listened to the phone call between the two leaders.

U.S. whistleblower laws exist to protect the identity and careers of people who bring forward accusations of wrongdoing by government officials. Lawmakers in both parties have historically backed those protections.

(AP)