South African police have arrested a priest in the capital, Pretoria, for allegedly conducting at least 600 fake marriages in the past year.
Some poor South African women also get married for money
The weddings are held so foreigners can acquire South African nationality.
Officials began investigations after unsuspecting women complained their wedding days had been ruined after they found out they were already married.
A nationwide advertising campaign is now advising South African women to check their marriage status.
Hendrik Uys Jansen, aged 39, is also a registered marriage officer, and according to police, held the fake ceremonies at his home in Pretoria.
"We have reason to believe that Jansen is part of a syndicate operating countrywide," said a police statement.
"His arrest follows several other recent ones nationwide as part of investigations into these syndicates," it said.
Reports say more than 3,000 women are now known to have been married off without their knowledge in the scam.
The BBC's Mohammed Allie in Cape Town, who has been investigating the scam, says it also involves poor South Africans who are paid to marry foreigners they have not met before.
One woman he spoke to says the first and only time she saw her so-called husband was at the Department of Home Affairs Offices on the day they were married.
The marriage was arranged by a local community worker whom she claims has been running a scam in her area.
"He came to me again and asked if I could get girls for him. I just had to approach them and ask... and they did it for the money because they were desperate as well," she told him.
Crime syndicates sell the fraudulent marriage certificates and residence permits for up to 5,000 rand ($833) each.
The buyers mostly come from Pakistan, Nigeria, Egypt, India, Bangladesh and Brazil, the home affairs department says.
The government has begun closing loopholes and is introducing a new immigration bill, our reporter says.