WASHINGTON (AP) — The Justice Department has embarked on a fresh investigation into one of President Donald Trump's chief grievances, issuing a flurry of subpoenas related to the U.S. government's inquiry into Russian interference in the 2016 presidential election, multiple people familiar with the matter said Friday.

The grand jury subpoenas issued out of the Southern District of Florida seek documents related to the preparation of the Obama administration's intelligence community assessment, made public in January 2017, that detailed how Russia waged a covert influence campaign to help Trump defeat Democratic nominee Hillary Clinton.

It was not clear whether the new inquiry might produce criminal charges or even what criminal allegation was being examined. But its mere existence underscores the extent to which Trump is determined to make good on his pledge to seek retribution over an election interference investigation that shadowed him before he took office in 2017 and continued to cast a cloud over much of his first term. It also comes as the Justice Department has investigated and in some cases prosecuted Trump’s political foes, including former FBI Director James Comey, who was fired by Trump months into his first term in the White House amid the Russia investigation.

The full list of people who were receiving subpoenas was not immediately known. But a person familiar with the matter identified some of the current, future or intended recipients as former CIA Director John Brennan as well as Peter Strzok and Lisa Page, two FBI employees who were involved in the Russia investigation and who traded pejorative text messages about Trump. Strzok, a top counterintelligence agent, was later fired and Page, an FBI lawyer, resigned. As many as 30 subpoenas were expected to issued, the person said.

The Trump administration has freshly scrutinized the intelligence community assessment in part because a classified version of it incorporated a summary of the “Steele dossier,” a compilation of Democratic-funded opposition research that was assembled by former British spy Christopher Steele and was later turned over to the FBI. That research into Trump's potential links to Russia included uncorroborated rumors and salacious gossip, and Trump has long held up its weaknesses in an effort to discredit the entire Russia investigation.

Multiple government reports, including bipartisan congressional reviews and a criminal investigation by former special counsel Robert Mueller, have found that Russia interfered in Trump's behavior through a hack-and-leak operation of Democratic emails as well as a covert social media campaign aimed at sowing discord and swaying American public opinion. Mueller's report found that the Trump campaign actively welcomed the Russian help, but it did not establish that Russian operatives and Trump or his associates conspired to tip the election in his favor.

Since returning to the White House, Trump has continued to rail against the Russia investigation and top administration officials, including FBI Director Kash Patel, CIA Director John Ratcliffe and Tulsi Gabbard, the director of national intelligence, have championed the release of years-old documents meant to try to discredit the investigation.

In July, for instance, Ratcliffe released a CIA report that identified what it said were tradecraft anomalies in the creation of the Obama administration's intelligence community assessment.

That report said the inclusion of a two-page summary of the Steele dossier in a classified annex of the intelligence community assessment — a decision pushed by the FBI — “implicitly elevated unsubstantiated claims to the status of credible supporting evidence, compromising the analytical integrity of the judgment.”