DALLAS — A Dallas man faces up to 20 years in federal prison for his role in what prosecutors call a more than $6 million diamond investment scheme.

Jay Bruce Heimburger pleaded guilty Tuesday in Dallas to mail fraud. Investigators say the 58-year-old Heimburger will be sentenced later over the scam from early 2011 until late 2013.

Prosecutors say a Houston man, 56-year-old Christopher Arnold Jiongo, in May pleaded guilty to wire fraud and awaits sentencing. The case continues against a third defendant.

Authorities say more than 75 investors in the purchase and resale of diamonds, on the international market, were scammed of about $6.4 million. Prosecutors say money and property were fraudulently secured.

A federal judge, during sentencing, could order restitution.