Federal prosecutors say seven Africans have admitted being part of a global fraud network that used online dating sites to reach potential victims.

A news release Friday said six Nigerians and a South African pleaded guilty this week to conspiracy to commit mail and wire fraud.

They're among 21 defendants in federal court in Gulfport, Mississippi. Investigators in Washington and New Orleans also were involved.

Documents with the guilty pleas show that the investigation started in 2011, when a Biloxi, Mississippi, woman told police that a man she'd met online through a dating website had asked her to repackage and reship cellular phones.

She let Homeland Security investigators use her email account to correspond with him.

According to court papers, investigators learned of more than 200 conspirators worldwide.