WASHINGTON - At least 105 foreign nationals suspected of terrorist involvement who might "pose a threat to national security" received visas granting them access to the United States this year because of lapses in a new background check system ordered by President Bush, according to government officials and documents.

Investigators for the General Accounting Office, who first uncovered the breaches, are trying to determine how many of them entered the United States and how many might be at large here, according to congressional officials familiar with the probe.

Compounding their fears, investigators believe the breaches typically were not discovered until five to six weeks after the visas were granted, so they had plenty of time to enter the United States and possibly disappear, according to officials familiar with the investigation.

The Justice Department and the FBI declined to comment.

Cam Simpson is a reporter for the Chicago Tribune.