The connections between Palantir and Cambridge Analytica were thrust into the spotlight by Mr. Wylie’s testimony on Tuesday. Both companies are linked to tech-driven billionaires who backed Mr. Trump’s campaign: Cambridge is chiefly owned by Robert Mercer, the computer scientist and hedge fund magnate, while Palantir was co-founded in 2003 by Mr. Thiel, who was an initial investor in Facebook.

The Palantir employee, Alfredas Chmieliauskas, works on business development for the company, according to his LinkedIn page. In an initial statement, Palantir said it had “never had a relationship with Cambridge Analytica, nor have we ever worked on any Cambridge Analytica data.” Later on Tuesday, Palantir revised its account, saying that Mr. Chmieliauskas was not acting on the company’s behalf when he advised Mr. Wylie on the Facebook data.

“We learned today that an employee, in 2013-2014, engaged in an entirely personal capacity with people associated with Cambridge Analytica,” the company said. “We are looking into this and will take the appropriate action.”

The company said it was continuing to investigate but knew of no other employees who took part in the effort. Mr. Wylie told lawmakers that multiple Palantir employees played a role.

Image Alfredas Chmieliauskas, a Palantir employee, suggested Cambridge Analytica scientists create an app to scrape Facebook data.

Documents and interviews indicate that starting in 2013, Mr. Chmieliauskas began corresponding with Mr. Wylie and a colleague from his Gmail account. At the time, Mr. Wylie and the colleague worked for the British defense and intelligence contractor SCL Group, which formed Cambridge Analytica with Mr. Mercer the next year. The three shared Google documents to brainstorm ideas about using big data to create sophisticated behavioral profiles, a product code-named “Big Daddy.”

A former intern at SCL — Sophie Schmidt, the daughter of Eric Schmidt, then Google’s executive chairman — urged the company to link up with Palantir, according to Mr. Wylie’s testimony and a June 2013 email viewed by The Times.