Washington (CNN) Even as House Republicans mount a vigorous defense of President Donald Trump amid the impeachment inquiry, some are growing uneasy about the role that Trump's personal lawyer Rudy Giuliani played in carrying out US policy with Ukraine -- and say there needs to be more investigation about his efforts.

Several Republicans who sit on the key committees say more needs to be learned about Giuliani's role, while also revealing new concerns about the continuing revelations that are emerging.

"I worry a lot about non-professionals pursuing diplomacy in the name of" American diplomacy, said Rep. Francis Rooney, a Florida Republican and former US ambassador under George W. Bush when asked about Giuliani. Rooney noted "more things keep coming up in the investigation" and the investigation should look at who "who else was involved."

"They called Watergate a witch hunt," Rooney noted.

Another Republican House member, who sits on one of the committees leading the impeachment probe, told CNN: "We have to see what his involvement is."

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