When a woman recently asked for a copy of her marriage license, the court clerk in suburban Atlanta's Gwinnett County had to break some unpleasant news: Her husband was listed as the groom in eight marriages in the county.

The husband was later arrested in September on suspicion of bigamy, just days after another man was charged in the same county with similar offenses. Two weeks later, a woman from nearby Decatur was charged with marrying six men in less than two years without ever dissolving her first marriage.

Federal immigration authorities are investigating whether the three defendants were part of a sham-marriage ring aimed at helping immigrants from Africa obtain their green cards, or permanent U.S. residency.

Immigration officials and prosecutors say phony green-card marriages are a common and growing crime, and they are cracking down.

"It took much more significance after 9/11," said Martin Ficke, agent in charge of the New York City office of Immigration and Customs Enforcement. "With a real green card, you get a lot more access. It's a major priority for ICE."

If the three defendants were part of a green-card scheme, that would not surprise Gwinnett County Probate Court Chief Clerk Marlene Duwell, who has seen plenty of suspicious things among the thousands of people she deals with each year.

Duwell said she has witnessed couples who couldn't converse with each other because of a language barrier, and marriage-license applicants who did not know their future spouse's last name or place of birth. Clerks reports their suspicions to police, which was what happened in the case of the man with eight wives.

Immigration officials focus on sophisticated moneymaking rings, not individuals doing someone else a favor, as in the 1990 romantic comedy "Green Card." In the movie, a Frenchman who wants a green card and a New Yorker who wants an apartment get married, only to fall in love.

Over the past year, authorities have busted large green-card marriage rings from coast to coast that made millions of dollars by providing spouses and fake documents to foreigners.

About one in five of the 3,494 identity and benefit fraud cases Immigration and Customs Enforcement investigated in fiscal year 2005 were marriage fraud, said agency spokesman Marc Raimondi. He said arrest figures were not immediately available.

However, authorities said arrests are on the rise, partly because immigration officials over the past three years have created task forces focused on fraud.

By marrying an American citizen, foreigners can win the right to stay and work in this country.

Within two years of the wedding, husband and wife are called in to be interviewed separately by an immigration officer who establishes whether the marriage is bona fide and, if so, grants a green card. The interviewer can ask anything: how they met, which side of the bed a spouse sleeps on, the color of his or her toothbrush.

While the process is long and expensive at about $5,000, it is, in many cases, easier than getting a green card through an employer. Nearly 260,000 spouses of U.S. citizens became permanent residents in 2005, up from fewer than 185,000 in 2003, according to the government.

Two especially large rings were broken up over the summer in Utah's Salt Lake County and New York City. In New York, a former immigration officer and his sister are accused of making more than $1 million over four years by providing hundreds of fake marriage documents and paying U.S. citizens to enter into sham marriages with foreigners.

In Utah, 24 people — most of them naturalized U.S. citizens from Vietnam — were charged with paying at least 46 U.S. citizens as much as $10,000 each to travel to Vietnam to marry Vietnamese people. The foreigners were charged $30,000 each.

The organizers took care of the smallest details: They made "couples" change their clothes over and over for a succession of pictures that would give the appearance of long-term relationships, wrote backdated "love letters," even bought a wedding ring for a couple who met 20 minutes before the ceremony, prosecutors say.

While some immigrants who enter into sham marriages might only want a better life in the U.S., others can exploit their green cards to move around freely and commit crimes, and even acts of terrorism, law enforcement authorities say.

"People may have gotten away with it in the past. But it's a much higher risk to participate in immigration crime than ever before," said Dustin Pead, the federal prosecutor in the Utah case.