Harendra Singh, the businessman at the center of the corruption scandal that has led to federal bribery charges against two top Nassau politicians, began his restaurant career modestly.

Singh, 57, who immigrated to the United States from India in 1979, opened an A&W restaurant 28 years ago in Bethpage. He and his wife, Ruby Singh, would go on to open dozens of restaurants stretching from Long Island City, to his flagship H.R. Singletons in Bethpage, to beach concessions in Brookhaven and Oyster Bay.

Last year his business holdings collapsed as Singh, deeply in debt, was accused of 13 federal charges, including bribing an Oyster Bay official to obtain millions of dollars of municipal loan guarantees. He has pleaded not guilty and is awaiting trial scheduled for January. He was released from jail in August. Sources have identified Singh as assisting federal prosecutors.

During his early years as a small businessman, he befriended Edward Mangano, who would later become Nassau County executive. In 1998, he was awarded an emergency contract to operate concessions at Oyster Bay’s town-owned golf course and would later obtain other town concessions.

His family started a nonprofit, the Raj and Rajeshwari Foundation, that raised money to provide healthcare in rural India. The foundation’s annual fundraising galas at the Oyster Bay-owned Woodlands catering hall became a who’s who of Nassau County politicians and contractors. Mangano and Oyster Bay Town Supervisor John Venditto were regular speakers at the galas.

Singh’s companies made regular campaign contributions to local politicians and committees, which in turn held campaign events at his restaurants, campaign finance records show. On Thursday, federal prosecutors alleged that Mangano and Venditto received discounts at Singh’s facilities and accepted limousine services and other bribes.

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Singh’s empire began to crumble when he bought the company that operated the Water’s Edge restaurant under a concession agreement with New York City in 2009, Newsday has reported. That transaction left the company owing pension obligations that resulted in $2.4 million in federal liens being filed against several of his companies.

With the lease ending in 2017, Singh donated thousands of dollars to New York City Mayor Bill de Blasio’s campaign, records show. Those donations and campaign events hosted at the restaurant are now the subject of a federal investigation with which Singh is cooperating, Newsday has reported, citing unnamed sources.

The restaurant closed last year as it fought eviction by the city in a rent dispute, Newsday has previously reported.

As his money problems mounted, Singh allegedly bribed Oyster Bay officials to guarantee millions of dollars in loans that prosecutors said were used for operating expenses of other businesses rather than the capital expenses at town facilities for which they were intended.

Oyster Bay is fighting three lawsuits from Singh’s lenders who are seeking to collect more than $17 million on disputed guarantees over defaulted loans.