David Friehling, a 49-year-old certified public accountant, is under scrutiny amid allegations that he was auditing the books for Bernard Madoff’s alleged $50 billion fraud.

The American Institute of Certified Public Accountants said Friehling was auditing -- and providing statements that he was auditing -- Madoff’s broker/dealer and securities firms, while at the same time telling regulators that he didn’t do any audits.

Friehling’s office, Friehling & Horowitz CPA, is now closed -- but the questions about his relationship with Bernie Madoff remain open. 

Investigators probing Friehling’s relationship with Madoff subpoenaed records from Friehling & Horowitz, all of which are due by Dec. 29.

Friehling’s lawyer declined to comment. Friehling himself would not speak to this reporter, who questioned him in person about the Madoff case -- but awaiting Friehling in his driveway brought out a relative of his, who doused the vehicle with a bucket of water.

Investigators are talking to Friehling’s retired partner, 80-year-old Jerome Horowitz, who lives in Palm Beach Gardens, Fla. A source familiar with the case says Horowitz worked for Madoff for years prior to his 1997 retirement.

Horowitz’s daughter Robin also worked at the firm. She married David after meeting him at Cornell University in the early 1980s.