Paul Singer, founder and president of Elliott Management Corp., provides financial support to the Washington Free Beacon, which paid a Washington research firm to start probing Donald Trump’s background in 2016. (Misha Friedman/Bloomberg)

A conservative publication said Friday it paid a Washington research firm to start probing Donald Trump's background — a move that set in motion a chain of events leading to the explosive dossier alleging ties between Trump associates and Russia.

In a statement, the Washington Free Beacon said it retained Fusion GPS to provide research on multiple Republican candidates in the 2016 presidential election. Two people familiar with billionaire GOP donor Paul Singer said he provides financial support to the publication. A spokesman for Singer's firm, Elliott Management, did not respond to requests seeking comment.

The Free Beacon said its research ended before Fusion GPS hired a former British intelligence officer, Christopher Steele, to produce a series of reports alleging links between Russia and those close to Trump. That occurred after the firm was retained by a lawyer for Hillary Clinton's presidential campaign and the Democratic National Committee.

"None of the work product that the Free Beacon received appears in the Steele dossier,'' said the statement from Free Beacon editor in chief Matthew Continetti and chairman Michael Goldfarb. "We stand by our reporting and we do not apologize for our methods.''

The Free Beacon's lawyers notified the House Intelligence Committee of its role in the matter Friday.

The website published a statement on Friday that said it paid Fusion GPS to research "multiple candidates in the Republican presidential primary, just as we retained other firms to assist in our research into Hillary Clinton." Since its inception in 2012, the website "has retained third-party firms to conduct research on many individuals and institutions of interest to us and our readers.''

Opposition research is nothing new in political races, or the corporate world, but it is not a common practice for a news website to hire out such work, which is often expensive. Firms like Fusion GPS can charge tens of thousands of dollars for research on a single subject.

After the Free Beacon stopped paying Fusion GPS, the research firm offered in April 2016 to continue researching Trump for the Clinton campaign and the DNC. The Free Beacon said it did not know at the time that the Clinton campaign and the DNC hired Fusion GPS later to continue the work.

The dossier — a collection of reports compiled by Steele that began in mid-2016 and continued after the election — cited sources familiar with the inner workings of the Kremlin, who said Russia had obtained compromising information about Trump, including lurid alleged details of his 2013 visit to Moscow for the Miss Universe Pageant. The Steele reports also alleged Russia had been working with Trump associates to help him with the election.

Trump has denied those claims, and called subsequent probes by the FBI and special counsel Robert S. Mueller III a witch hunt. Officials have said that the FBI has confirmed some of the information in the dossier. Other details, including the most sensational accusations, have not been verified and may never be.

U.S. intelligence agencies later released a public assessment, which concluded that Russia intervened in the 2016 election to aid Trump. The FBI has been investigating whether any Trump associates helped the Russians.

For months, House Republicans have been pressuring Fusion GPS to identify who paid for the dossier.

Last week, Fusion GPS executives invoked their constitutional right not to answer questions put to them by the House Intelligence Committee. Previously, the firm's founder, Glenn Simpson, had spent 10 hours answering questions from the Senate Judiciary Committee.

While questions about the mystery clients have now been answered, Republicans on the House Intelligence Committee are still pressing to find out how much Fusion GPS was paid, and how much, in turn, that firm paid Steele.