An ex-FBI employee was arrested yesterday in Brooklyn on charges that she swindled nearly a dozen alien residents out of thousands of dollars by trying to sell them green cards.

The government says that, in a play for more than $40,000 in cash, Brooklyn resident Rosana Frederick, 57, told 11 people over a nine-month period in 2001 that she was a federal agent and could obtain permanent resident documentation – green cards – for them.

According to the charges, Frederick told some of the alien residents that she worked for the FBI, and others that she worked for the Immigration and Naturalization Service.

Frederick, who is charged with impersonating federal officers, faces a maximum of three years in prison and a $250,000 fine if convicted. She was released on bond after being arraigned yesterday in federal court in Brooklyn.

Reached by phone at their home in Brooklyn, Frederick’s son said the charges against his mother were untrue and that she would plead not guilty. Frederick declined comment.

This is the second time Frederick has been accused of fraud. In December 1992, a jury found her guilty of extorting money from aliens while she worked as a clerk for the FBI. She served 18 months in prison for the conviction.

According to an affidavit unsealed yesterday, Frederick first offered to obtain a green card for a livery cab driver in January 2001. She told the driver she was retired from the FBI and had contacts at the INS. After the driver paid Frederick $2,500 to get a card for his cousin, she allegedly offered him $500 to refer people in a similar situation to Frederick.

The driver collected money for Frederick, according to the affidavit, and recruited his uncle to join the scheme. By the summer, the operation allegedly included eleven people who had each paid up to $8,800 for a green card.

After making appointments for August and September to distribute the green cards, Frederick fled to her native Trinidad and none of her clients received the cards or heard from her again, the affidavit says.

In all, the government says Frederick collected more than $43,500 from the eleven aliens to whom she promised green cards.

Her arrest culminated a joint investigation by the U.S. attorney’s office in Brooklyn, the FBI, and the inspector general. In a statement, the U.S. inspector general, Glenn Fine, said the arrest indicated the government was serious about curbing abuses of authority.

“No one seeking access to services from the Department of Justice should be confronted with anyone seeking a payoff,” Mr. Fine said. “This case shows that the Office of the Inspector General takes seriously any allegation of abuse of Department of Justice authority.”