According to Mark Zaid, among the lawyers for the first whistle-blower, they had spoken to the intelligence community's inspector general, who is reportedly probing the first person's allegations, on the matter, the BBC reported.
No details are known about the second whistle-blower's claims, but Zaid told ABC News that the the person claimed to have first-hand information about the allegations against Trump, it said.
The Democrats contend that Trump improperly sought help from Ukraine to boost his chances of re-election in 2020 polls, asking Ukrainian President Volodymyr Zelensky for some damning information about his prospective Democrat rival, former Vice President Joe Biden, in a phone call on July 25.
The impeachment inquiry stems from the call, which was flagged up by the initial whistle-blower in August, reporting concern about it in a letter to Senate committee chairpersons.
The whistle-blower alleged that the White House moved to "lock down" all details of the phone call, and its transcript was not stored in the usual computer system.
A report in the New York Times earlier this week indicated that a another person who had "more direct information" about the events surrounding the call was considering come forward. It is not yet known if this is the person that Zaid referred to.
The White House has not commented on the matter but Trump's personal lawyer Rudy Giuliani, in a tweet, said that he was not surprised there was another "secret source", calling the inquiry politically motivated.
Trump has repeatedly rejected the original complaint, calling it a "witch-hunt".
( With inputs from IANS )