The Justice Department said yesterday it was investigating the North Carolina Republican Party for possible violations of civil rights laws after finding that a "ballot security" program there had sent out over 100,000 postcards that "falsely mislead" voters.

State Republican officials have acknowledged that the mailings went to voters in predominantly Democratic precincts in 29 counties. Amy Casner, a spokeswoman for the Justice Department's civil rights division, said department officials were "gathering information" to determine if the mailings were racially motivated and could file a lawsuit against the party if they find they were targeted at black voters.

Casner said the mailings made "false and misleading" statements to recipients that were "almost intimidating." The cards warned voters that if they had moved to another residence within the past 30 days, they were not eligible to vote, an assertion Casner said was untrue. The cards also said: "It is a federal crime, punishable by up to five years in jail, to knowingly give false information about your name . . . or place of residence to an election official."

The postcards have become an issue in the Senate race between Sen. Jesse Helms (R-N.C.) and Democratic challenger Harvey Gantt, with Democrats charging the mailings constituted "blatant intimidation" of black voters.

John Dunne, assistant attorney general for civil rights, said he had secured a pledge from state GOP Chairman Jack Hawke that no voter will be challenged at the polls because of information gleaned from the mailing -- for example, that the voter's address is incorrect.

The civil rights division dispatched a team of lawyers to North Carolina to observe the voting today, and plans a special hotline to receive complaints.

Casner said department officials were "not prepared to say" at this point that the postcards were targeted at black voters. But an official of the Gantt campaign said yesterday it knew of several instances in which the postcards were sent to biracial couples addressed only to the black member of the family.

"I think this is finally going to end up helping us. Clearly, they've gone too far," said Crawford Crenshaw, a Gantt fund-raiser.

In a related development, a federal judge ruled in Newark, N.J., that the Republican National Committee was not involved "directly or indirectly" with the postcard mailing, as was charged in a lawsuit by the Democratic National Committee.