The U.S. Justice Department has tightened the enforcement of foreign student visa rules over the past three months following a January 2 riot by Iranian students in Beverly Hills, Calif.

To maintain or renew a visa, a student may not hold a full-time job and must be enrolled in a full-time educational program. John Russell, a Justice Department spokesman, said Thursday students who violate these conditions may now face immediate deportation proceedings instead of warnings.

He added that since January, the Justice Department has deported four students because of the stricter policy.

One Immigration and Naturalization Service (INS) spokesman said Friday that out of about 250,000 foreign students in the country, as many as 40,000 may violate the rules.

The new policy has not yet affected foreign students at Harvard who generally follow federal regulations, officials at the International Office said Thursday.

The Justice Department had relaxed student visa regulations on January 1 by allowing foreign students enrolled in programs requiring several years of study to remain in the country while completing their studies without annually renewing their visas.

Russell said Atty. Gen. Griffin Bell, prompted by the Iranian riot, directed the INS to check the number of foreign students in American colleges. "Our information was about seven months behind, so we asked colleges to give us the number of foreign students enrolled with them," Russell said.

Sonya B. Roll, an INS officer in Boston, said Friday students renewing their visas would have to be interviewed by the INS first.

The interviews, ordered by a Justice Department directive in early February, help the INS verify that the student has not been "illegally employed" or behaved "in a manner inconsistent with his/her presence in the United States as a student," an INS spokesman said Friday.

Eugene R. Chamberlain, adviser to foreign students at the Massachusetts Institute of Technology, said Thursday that the INS had asked student advisors at colleges to conduct the interviews themselves.

"We strongly objected to conducting the interviews, and a considerable national write-in campaign resulted. Our point was made and the INS said they would conduct the interviews," Chamberlain said.

"Student advisers were never forced to conduct the interviews; we merely gave them the option," Roll said.

One University official said Thursday the visa enforcement policy is not new, but that after the Iranian riot the INS wanted to re-affirm its position publicly. "The INS was embarrassed that they really didn't know what foreign students were doing," the official said.