NEW YORK (CBSNewYork) — A restaurant owner central to the case against Nassau County Executive Ed Mangano and his wife is also a major donor to Mayor Bill de Blasio, whose fundraising activities are under investigation by federal and state authorities.

Harendra Singh was named as “co-conspirator #1” on the indictment of Mangano and others.

He also donated thousands of dollars to de Blasio when he ran for office, and his generosity was rewarded with a number of key appointments, CBS2’s Marcia Kramer reported.

U.S. Attorney Preet Bharara, who is probing de Blasio’s campaign fundraising activities, is trying to determine if there were any quid-pro-quos, with donors receiving favors in return for their contributions.

More than $54,000 were donated to de Blasio’s mayoral campaign and transition committee by Singh and various relatives. Singh was then appointed to a number of prestigious posts on de Blasio’s inauguration committee, the committee backing the city’s failed bid to get the Democratic National Convention, and the committee to support and raise money for the mayor’s pre-k initiative called UPKNYC, Kramer reported.

Expected to be of particular interest to investigators are Singh’s problems with his Queens restaurant, The Water’s Edge, and the city’s attempt to evict him for owning $1.4 million in rent underpayments.

Singh was also previously indicted for trying to bribe a former Oyster Bay employee.

A spokesperson for de Blasio said Singh got no special treatment.

“The administration is absolutely confident that we’ve acted appropriately at all times,” the spokesperson said. “We don’t do pay-to-play. Out of an interest in protecting the integrity of an ongoing review, we can’t comment further at this stage.”

Published reports in the New York Times said Singh was cooperating with investigators in the de Blasio case, but Singh’s lawyer spoke only of the Nassau County case, saying he would provide his client “with the most powerful legal defense possible.”