Westchester County Executive Rob Astorino is defending a mysterious campaign contribution made to a political party he started last year.

Astorino is referring to a donation made to his party by the Institute for Municipal Safety Research LLC, a company with no website or phone number, and appears to be registered out of state.

However, it filed its address with the state Board of Elections at a White Plains law firm run by the Rockland Republican chairman who News 12 has been told represents the owner of the company.

The Reform Party started by Astorino last year received a $107,000 donation from that company a few months ago. The money went directly into attack ads against a Democratic town supervisor in Clarkstown.

While Astorino says there's nothing wrong, Democrats are asking the state and federal prosecutors to investigate.

Republican George Hoehmann, who is running for town supervisor in Clarkstown, did not return calls for comment. His campaign manager says it did not directly receive the donation, so it wouldn't be responsible if any illegalities were uncovered.