(Reuters) - The federal investigation into Russian meddling in the 2016 U.S. presidential election and potential collusion by Donald Trump’s campaign has targeted - directly or indirectly - a growing group of presidential associates.

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As Special Counsel Robert Mueller presses on with his Russia probe, the following is a list of people who have been indicted or are being investigated. The court documents related to Mueller's investigation are at www.justice.gov/sco .

Trump has denied any collusion by his campaign and has long denounced the Mueller probe as a witch hunt. Mueller told Trump’s attorneys in March he was continuing to investigate the president but did not consider him a criminal target “at this point,” the Washington Post reported in early April.

Michael Cohen, Trump’s longtime personal lawyer, is being investigated by federal prosecutors in Manhattan. Cohen’s lawyer, Stephen M. Ryan, said U.S. prosecutors conducted a search on April 9 that was partly a referral by Mueller’s office. Federal prosecutors are investigating Cohen for possible bank and tax fraud, and possible campaign law violations in connection with a payment to a porn actress and perhaps other matters having to do with foreign support to Trump’s 2016 campaign, a source familiar with the investigation said.

Michael Flynn, a former national security adviser to Trump who was also a close campaign aide, pleaded guilty in December to lying to FBI agents about his contacts with Russia and agreed to cooperate with Mueller’s investigation.

Paul Manafort, a former Trump election campaign chairman, is facing two indictments in different federal courts brought by Mueller. Charges against him include conspiring to launder money, failing to register as a foreign agent in connection with his lobbying for the previously pro-Russia Ukrainian government, bank fraud and filing false tax returns. Manafort has pleaded not guilty to all charges and argued that Mueller has overstepped his authority. On June 15 a judge revoked Manafort’s bail and sent him to jail to await trial, citing new charges that he sought to influence the testimony of two government witnesses.

Rick Gates, a former deputy campaign chairman, pleaded guilty in February to conspiracy against the United States and lying to investigators, and agreed to cooperate with the Mueller probe.

George Papadopoulos, a former Trump campaign adviser, pleaded guilty last fall to lying to FBI agents about his contacts with Russia. According to documents released with his guilty plea, Papadopoulos offered to help set up a meeting with then-candidate Trump and Russian President Vladimir Putin. He has been cooperating with Mueller.

Alex Van der Zwaan, a lawyer who once worked closely with Manafort and Gates, pleaded guilty in February to lying to Mueller’s investigators about contacts with an official in the Trump election campaign. Van der Zwaan, the Dutch son-in-law of one of Russia’s richest men, was sentenced on April 3 to 30 days in prison and fined $20,000.

Thirteen Russians and three Russian entities were indicted in Mueller’s investigation in February, accused of tampering in the 2016 election to support Trump. The Russian government has repeatedly denied meddling in the election.

Richard Pinedo, who was not involved with the Trump campaign, pleaded guilty in a case related to the Mueller probe in February to aiding and abetting interstate and foreign identity fraud by creating, buying and stealing hundreds of bank account numbers that he sold to individuals to use with large digital payment companies. Pinedo “made a mistake” but “had absolutely no knowledge” about who was buying the information or their motivations, his lawyer said. Sources familiar with the indictment said Pinedo was named as helping Russian conspirators launder money as well as purchase Facebook ads and pay for rally supplies.

Konstantin Kilimnik, a Manafort aide and political operative with alleged ties to Russian intelligence, was charged on June 8 with tampering with witnesses about their past lobbying for Ukraine’s former pro-Russian government.