Swalwell told Yahoo News that the House Intelligence Committee needed to seek testimony from Felix Sater, a Russian-born developer and Donald Trump associate, as well as Trump.
"This is a bright light in an ever growing constellation of contacts between Donald Trump and Russia,” Swalwell said of the new reports of a Trump Tower in Moscow, The Hill reported.
Trump’s company and investors signed a letter of intent to open up a massive development as part of the Trump brand but dropped the deal in January 2016 after they failed to get the land and permits to launch the project, The Washington Post reported Sunday.
Sater had reportedly also encouraged Trump to visit Moscow to hear about the proposal and promised he could get Russian President Vladimir Putin to say "great things” about Trump, according to the Post.
Developers first began discussing a deal in 2015, but it's unclear if Trump was aware of the negotiations.
The report comes amid an ongoing probe led by special counsel Robert Mueller into possible collusion between members of Trump's team and Russia's efforts to influence the presidential election.
Swalwell said Tuesday that Sater is a "relevant witness” who could have been a "pivotal player” between the Trump campaign and the Russian government. He also told Yahoo News that Trump is also a relevant witness.
"We don’t want to be reckless,” Swalwell told Yahoo. "But that should be on the table. My belief is we have to hear from all relevant witnesses, and it does look like he [Trump] is likely relevant.”