The owner of a pizza chain who was found guilty earlier this year for blackmailing undocumented employees into working long hours at his restaurants, sometimes without pay, has been sentenced to more than eight years in federal prison, the U.S. Attorneys Office for the District of Massachusetts announced Monday.

Stavros Steve Papantoniadis, 49, the owner of Stashs Pizza, was sentenced to eight and a half years behind bars and will be required to pay a $35,000 fine following his release, according to the announcement. Federal officials in Massachusetts said Papantoniadis hired undocumented people in order to exploit them.