Mayor Bill de Blasio has not commented on a widening federal investigation into his role in Democratic fundraising efforts.
Sources tell NY1 the State Board of Elections conducted its own inquiry, and found the Mayor's team appears to have knowingly and intentionally violated campaign finance laws during the 2014 State Senate campaign.
The Mayor was part of fundraising efforts for three unsuccessful State Senate races upstate.
A source familiar with the investigation says it believes the Mayor's team circumvented donation limits for individual campaigns by funneling money through county political committees, which have much higher limits.
Investigators say donations from unions, developers, and businesses totaling hundreds of thousands of dollars were processed in this way, which can also disguise the identity of donors.
The Board of Elections referred the case to the Manhattan District Attorney's office earlier this year.
NY1 reached out the DA's office but they declined to comment.
The mayor has repeatedly maintained he and his staff have done nothing illegal.