Florida Sen. Marco Rubio, a member of the Senate intelligence committee that is currently investigating Trump’s team’s ties to Russia, said Sunday during a “Meet The Press” interview that he has seen “no evidence” to support Trump’s claims that were laid out in a series of tweets early Saturday morning.

“I’d imagine the President and the White House in the days to come will outline further what was behind that accusation,” Rubio said. “The President put that out there, and now the White House will have to answer as to exactly what he was referring to.”

And while many prominent Republicans have not addressed the topic, a few others joined Rubio in asking the President to release more information regarding his allegations, which Trump likened in a tweet to “Nixon/Watergate.”

“It would be more helpful if he turned over to the intelligence committee any evidence he has,” Maine Sen. Susan Collins, who is also a member of the Senate intelligence committee, said Sunday on CBS’s Face the Nation.

Arkansas Sen. Tom Cotton echoed his colleagues during an interview on Fox News Sunday. “It doesn’t mean that none of these things have happened, just means I haven’t seen them yet,” he said.

Trump has not clarified the source of his information, but many have pointed to a Brietbart News story that was broadcast Friday about the FBI obtaining warrants to monitor his campaign as part of an investigation into its alleged Russian ties.

Press Secretary Sean Spicer called on Congress to conduct a probe and called the news “very troubling” in a statement Sunday.

House Intelligence chairman Devin Nunes said on Sunday that his panel will include Trump’s allegations into his current investigation of Russia meddling in the 2016 election. The committee “will make inquiries into whether the government was conducting surveillance activities on any political party’s campaign officials or surrogates,” Nunes said in a statement.