Key political allies of Mayor Bill de Blasio have been subpoenaed in connection to a growing federal and state investigation into his fundraising activities.

Emma Wolfe, the mayor’s chief political aide, and Ross Offinger, his top fundraiser, were subpoenaed as investigators sought documents related to the mayor’s efforts to increase the Democratic presence in the state senate and his fundraising for a nonprofit set up to advance his agenda, the Wall Street Journal reported.

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“City Hall has been subpoenaed by the New York County District Attorney’s Office and the U.S. Attorney’s Office for the Southern District, and we are fully cooperating with the investigation,” Maya Wiley, counsel to the mayor, was quoted by the New York Daily News, adding that the mayor has not been served.

BerlinRosen, a consulting firm that has worked on de Blasio’s political campaigns, was also subpoenaed, according to the Wall Street Journal. The firm’s co-founder, Jonathan Rosen, is considered a top adviser to the mayor.

“We’re proud of the work we do for our clients,” Rosen was quoted by the Daily News. “We have acted appropriately and in accordance with the law at all times.”

Earlier, a report from New York’s Board of Elections alleged “willful and flagrant” violations on the part of the mayor and his allies in an effort to evade contribution limits and disguise contributors’ true names as they aimed to build a Democratic majority in the senate, according to published reports.

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In a rebuttal to the Board of Elections report, a lawyer for de Blasio said the allegations were politically motivated, reports stated. De Blasio has said that the Board of Elections accusations were “outrageous” and that he did nothing wrong.