SAN DIEGO (AP) - U.S. immigration authorities arrested nine people early Wednesday as part of a new enforcement program intended to track foreign students from the Middle East who entered the United States on valid visas but are no longer in school.

Agents from the Immigration and Naturalization Service fanned out around the San Diego area in the morning to locate and interview about 50 people who appeared to be violating the terms of their visas, INS spokeswoman Lauren Mack said.

None of those arrested is suspected of involvement in the Sept. 11 attacks.

Mack said the crackdown was a response to the agency's need to do more to track foreign students after it was revealed that one of the terrorists, Saudi Arabia native Hani Hanjour, entered the country as a student.

Authorities began compiling a database of the nearly 600,000 foreign students at U.S. colleges and universities after the 1993 World Trade Center bombing. That effort languished amid opposition from school officials who believed it would hurt student recruitment, would be too bureaucratic and be seen as intrusive.

In recent weeks, INS officials in San Diego began meeting with representatives of about 35 schools in the region, including the University of California, San Diego. They checked records of students from nations designated as "of special interest" by law enforcement authorities. Agents sought this morning to interview students born in Iran, Iraq, Sudan, Pakistan, Libya, Saudi Arabia, Afghanistan and Yemen.

About 90 percent of the students listed in INS records as being at local education institutions were enrolled. About 50 were not.

Agents began visiting their addresses of record to find them in the enforcement action that began at 5 a.m.

After visiting more than a dozen homes, they arrested nine men and women, including the brother of one student, Mack said. Further information on those arrested was not immediately available.

At some locations, authorities found the addresses listed on visa documents were incorrect or the person had never lived there. Others were homes of families who have hosted a number of foreign students over the years.

The crackdown was believed to be the first of its kind in the nation, Mack said.

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