Kamala Harris' ally has found himself at the center of a scandal over alleged ties to China.
An investigation has been launched against US Vice Presidential candidate Tim Walz.
The work is being carried out by the House Oversight Committee of Congress, Fox News reports.
Suspicions about Walz and his contacts with Chinese representatives fell during work related to the investigation of military and political operations of the Communist Party of the People's Republic of China against the United States.
Democrat Walz is among those who may act in Beijing's interests.
If he were to hold a high political position in Washington, he could undermine US sovereignty, Republicans complain.
However, information about the investigation against Walz has not been officially confirmed.
Fox News cites a letter sent by the House Oversight Committee to FBI Director Christopher Wray.
It was previously revealed that in 2005, Walz violated military service rules to resign several months before his unit was deployed to Iraq.
