Immigration agents arrested 10 people Wednesday in a search for foreign visa holders who are not enrolled in school, the government's first crackdown since Sept. 11 on foreign students who abuse their visas.

The early-morning sweep across San Diego County sent agents of the U.S. Immigration and Naturalization Service to the homes of about 50 people from eight countries in the Middle East, Africa and central Asia.

Officials said the action probably will be followed by similar enforcement in other spots across the country as part of a push to repair gaps in the system for tracking foreign students.

"We all feel the urgency of taking some action to straighten out the whole foreign student visa process," said an INS official in San Diego, who was barred by superiors from speaking on the record. "It's very poor. We don't have an effective system."

The students sought Wednesday were from eight countries deemed by the U.S. government to have terrorist links. They are Iran, Sudan, Syria, Pakistan, Libya, Saudi Arabia, Afghanistan and Yemen.

Immigration officials and the few FBI agents who helped them refused to name the 10 men and women detained Wednesday. One was released after proving that he was enrolled. The others are being held on administrative grounds and are subject to deportation, though they could appeal a deportation order.

Officials said one detainee could face criminal charges.

None of the visa holders sought or detained Wednesday were suspected of having ties to the terror attacks, the INS official said. "We did not have information going into this that any of these individuals represented a security threat."

Muslim activists in San Diego decried what they said was government profiling of Middle Eastern students. "These people have nothing to do with Sept. 11 and we should make that clear," said Mohamad Nasser, president of the San Diego chapter of the Muslim American Society. "I see this as a direct attack on Middle Easterners."

Nasser said that although some students from the Middle East undoubtedly overstay their visas, they represent a small share of violators. "I'm not justifying what they've done. But there's a lot more people out there not from the Middle East and they're not being targeted."

INS officials said the San Diego action represented an early step in a national campaign. "To protect national security, students from countries designated by the United States as supporting terrorist networks are among the first group to be scrutinized," said Bill Strassberger, a spokesman for the INS in Washington, D.C. "As this goes on, we're going to look at other foreign students. This isn't over today."

The terror attacks put an unwelcome spotlight on the Muslim community in San Diego, which had been home to at least two of the Sept. 11 hijackers. Four Middle Eastern men who lived in San Diego and a fifth who attended San Diego State University were subsequently arrested as material witnesses.

Officials said checks of several hundred student-visa holders from the eight countries found nearly all to be in compliance with the law.

During the past month and a half, agents contacted 35 schools to confirm enrollments of students and won the help of school officials, they said. Overall, about 10,000 foreigners hold student visas to attend colleges, universities, vocational and language schools in San Diego and Imperial counties.

Officials for UC San Diego and San Diego State University said they did not know if any current or former students were among those arrested, but said they did not believe so.

Barry Garron, spokesman for the San Diego Community College District, said his district reported that 10 of its 500 international students had not attended classes this semester. Garron said he did not know if any of those students were included in the arrests.

At some homes checked by INS agents, residents reported that the person sought had left the country or had never lived there. Some addresses were inaccurate.

Immigration officials and higher education representatives recently acknowledged serious flaws in the nation's system of screening applicants and monitoring the 500,000 foreign students in the United States. Calls for reform came after revelations that one of the Sept. 11 hijackers, Saudi native Hani Hanjour, entered the United States on a visa to study at a language school in Oakland, but never showed up for classes, officials said.

Immigration officials said loopholes in the current system mean that they do not know how many foreigners remain after their student visas expire, or whether a particular foreign student registered at the sponsoring school.