The U.S. Immigration and Naturalization Service has launched a review of the thousands of cases of immigrants with criminal histories who have been jailed pending deportation, and begun releasing some of those whom officials decide are neither dangerous nor likely to flee future court hearings.

The systematic review follows a series of at least 12 federal court rulings across the country against the previous INS policy of detaining all people eligible for deportation for their crimes, regardless of whether they had completed their original sentences long ago, received suspended sentences or never received any jail sentence.

Officials said that only a small fraction of the estimated 15,000 immigrants with criminal records in INS custody at any time may qualify for release under the new policy, and that the INS will continue with deportation proceedings against them after they are released.

But immigrant rights advocates hailed the decision to scrap the mandatory detention rule as a victory in their campaign against the 1996 laws expanding the categories of crimes for which immigrants can be deported. The laws also have been under attack because they stripped judges of the power to grant exceptions and were applied retroactively.

The new INS review consists of two parts. One, which began last month, covers immigrants who completed their original sentences before the 1996 laws took effect. The other covers immigrants who have been jailed indefinitely because their countries of origin refuse to take them back. The INS began that portion of the review on an informal basis in April, but issued uniform, national rules for it on Friday.

Rep. Lamar S. Smith (R-Tex.), chairman of the House Judiciary immigration subcommittee, has not objected to the review. But he has urged the INS to exercise extreme caution and threatened to hold the agency accountable "any time one of these individuals commits a subsequent crime."

Among those who have benefited from the review is Assegedech Biya, a 36-year-old Ethiopian who lives in Alexandria. She had been in the Rappahannock Regional Jail in Fredericksburg for more than six months, ever since INS agents showed up at the McLean hotel where she worked and said they were going to deport her for a shoplifting conviction.

She tried to steal clothes for her children five years ago, was caught, convicted of felony larceny and placed on probation. The theft, Biya said, was a desperate reaction to an abusive husband who had been withholding money from her and who later pleaded guilty to domestic assault and battery.

Now, he has the children. And until Friday, when the INS released her after inquiries about her case from The Washington Post, she had been stuck in jail.

"I came here to save my life," said Biya, who fled torture and imprisonment in her homeland and sought asylum in the United States in 1992. "Now I know there are no human rights here. How can you separate a mother and her children like this?"

Stories of individual hardship such as Biya's have been surfacing ever since Congress passed the 1996 laws. Now, immigrant rights advocates say, momentum appears to be building for Congress to do something about them.

"We've never had such a good opportunity to get some of these laws overturned," said Jeanne Butterfield, executive director of the American Immigration Lawyers Association. "There are thousands of stories like [Biya's], and it's building to a critical mass. . . . Most members didn't understand what they had wrought, and now they're beginning to realize that maybe they went too far."

Any effort to change the 1996 laws must clear an obvious hurdle: There's not much of a constituency for helping criminals, much less immigrants who are criminals. In addition, because people can be deported for crimes ranging from murder to drunken driving, it's unclear how many of them are people like Biya and how many are more serious felons.

INS spokesman Russ Bergeron said nearly half of the 55,869 criminal immigrants deported last year were convicted of drug offenses, and about 5,500 of the deportees were legal residents.

Still, some supporters of the 1996 laws are having second thoughts.

For example, Rep. Bill McCollum (R-Fla.), a conservative Judiciary Committee member considered tough on immigrant crime, has filed a bill to stop the deportation of a convicted Canadian thief who is the son of a local GOP official in his district. He is considering additional legislation.

In addition, the INS itself has called on Congress to restore some of the power of judges to review these deportation cases. Rep. Lincoln Diaz-Balart (R-Fla.) is pushing a bipartisan bill with more than 60 co-sponsors to do that. "This is gathering steam because more and more cases are coming to people's attention," he said.

One of those involves Rick Siridavong, 23, a Springfield resident whose family fled to the United States from Laos when he was 5. Siridavong applied for citizenship last year -- "to show my appreciation for this country" -- and ended up in jail.

Five years ago, Siridavong had been sentenced to probation and community service for stealing a car radio. He didn't realize the act made him deportable, and he openly admitted the conviction on his citizenship application. INS agents responded in February by going to his home and handcuffing him in front of his mother.

There was another wrinkle in Siridavong's case: A handful of countries don't accept criminal deportees, including Cuba, Vietnam, Cambodia -- and Laos. As a result, he faced the prospect of being detained indefinitely, like an estimated 3,500 other "lifers" in INS custody.

He was placed in a room at the Virginia Beach jail with about 30 other criminal deportees. About half of them were serious criminals, he said. But he said the rest were people like himself: a man who once stole a carton of cigarettes, another who removed a "parking boot" from his car, someone who bounced several checks.

"I was pretty depressed, and I was angry that the government could do this," he said. "We tried to get Canada or Australia to accept me. I mean, I'd rather go someplace I knew nothing about than stay locked up in there. It was terrible."

After nearly five months' incarceration, a judge ordered Siridavong released on $1,500 bond in July. While Siridavong sat in jail, lawyers across the country continued to challenge the 1996 laws. Cuban deportees being held indefinitely by the INS in the Miami area staged a hunger strike.

As for Biya, INS spokeswoman Ernestine Fobbs said it was only a coincidence that she was released a day after The Post asked about her case. But Biya's immigration advocate, Chris Einolf, said he tried to get her released weeks ago and believes The Post's interest expedited the process.

Biya said she will stay at a women's shelter until she finds a new home and job, adding that she will try to regain custody of her children. But she is worried because she still could be forced to return to Ethiopia, where she said she spent two months in prison and was beaten and tortured with electric shocks for her political activities.

"It doesn't make any sense," she said. "This isn't the American dream. This isn't my dream."