Federal prosecutors hit New York Congressman Michael Grimm on Monday with a 20-count indictment that includes fraud charges, wrapping up years of investigation into the Republican lawmaker’s business dealings and campaign financing.

The charges were related to a Manhattan health-food restaurant in which the lawmaker invested before taking office, and they were unsealed on Monday. The congressman allegedly underreported income at Healthalicious, the indictment stated. Other charges include perjury, wire and mail fraud, employing illegal immigrants, obstruction of justice, and conspiracy to defraud the United States.

Grimm, a former FBI agent and U.S Marine, represents Staten Island and southwest Brooklyn. He surrendered to authorities at an undisclosed location on Monday morning and is expected to be arraigned later the same day at a federal court in Brooklyn. The FBI probe began two years ago with a focus on Grimm’s campaign financing for his 2010 race, but it later shifted to the health-food restaurant Healthalicious, in which he began investing after leaving the FBI in 2006.

“Grimm made the choice to go from upholding the law to breaking it. In so doing, he turned his back on every oath he had ever taken,” said United States Attorney Loretta Lynch. “Even after his return to public service, when called to account for his actions and questioned under oath Grimm went for the cover up and lied about his role in his own business.”

Court documents allege that Grimm "intentionally" hired an unspecified number of illegal immigrants. It's believed that the congressman hid more than $1 million in income from Healthalicious and hundreds of thousands of dollars in employees' wages.

If convicted, Grimm could face up to 20 years in prison for each mail and wire fraud charge and for obstruction, according to the FBI. The health care fraud charge could result in 10 years imprisonment, and Grimm faces five years for conspiring to defraud the government and for perjury.

Two of Grimm’s fundraisers have already been charged in connection with his campaign contributions. That matter is still under investigation, and Grimm hasn't been accused of any wrongdoing in relation to that case. However, USA Today reported that the 44-year-old congressman acknowledged receiving $250,000 to $300,000 in campaign donations from the followers of Israeli rabbi Yoshiyahu Yosef Pinto. Some of Pinto’s followers said they illegally contributed tens of thousands of dollars, including gifts through straw donors, to Grimm’s campaign.

The restaurant is allegedly linked to an Israeli fundraiser who was a liaison between the lawmaker and the rabbi. That liaison, Ofer Biton, pleaded guilty to immigration fraud charges in August, the Associated Press reported. Diana Durand, a woman who was romantically linked to Grimm, has been indicted for allegedly using straw donors to make illegal contributions and for making false statements to the FBI.

Grimm was among the class of Tea Party Republicans elected in 2010, and he is currently seeking re-election. He last made headlines in January when he threatened to physically harm NY1’s Washington reporter, Michael Scotto, who asked the congressman about the investigation. Grimm has since apologized.

The congressman’s office did not respond for a request for comment from International Business Times. However, his spokesman told ABC News in a statement that Grimm won’t resign.

“When the dust settles, he will be vindicated," the spokesman said. "Until then, he will continue to serve his constituents with the same dedication and tenacity that has characterized his lifetime of public service as a Member of Congress, Marine Corps combat veteran, and decorated FBI Special Agent.”