Nearly 200 people were turned away after trying to enter the country on student visas last month when their names failed to show up in the government's new database of foreign students, a Homeland Security Department (search) official said Tuesday.

One of the 190 cases has led the agency to investigate a possible conspiracy to bring groups of foreign students illegally into the United States, said Asa Hutchinson (search), the department's undersecretary for border and transportation security.

Universities, schools and other institutions that enroll foreign students had until Aug. 1 to enter identifying information of all enrolled foreign students into the Student Exchange Visitor Information System (search), or SEVIS.

Hutchinson said border security officials contacted schools when a student's name did not appear on the foreign student tracking system. If the school didn't have the required immigration forms from the student, the student was refused entry.

"It's not just a matter of a glitch in the system," he said. "They were really trying to come in under false information. That does not mean they are terrorists, but it certainly poses a challenge to the integrity of our system and potential danger to our country."

Hutchinson said about 600,000 foreign students returned to the United States for the fall and more than 6,400 schools have students registered in the system.

Congress authorized the foreign student tracking system after the Sept. 11, 2001 terrorist attacks. Fifteen of the 19 Sept. 11 hijackers entered the U.S. legally on travel visas. Three were admitted with business visas and one on a student visa.

Hutchinson declined to give details about the investigation into the possible conspiracy case but said it was "fairly routine in our business that we have fraudulent use of documents and investigations with regards to that."

The 190 students who were turned away would have passed background and name checks in the process of applying for their visas, Hutchinson said, adding that information barring some students' entry to the United States may have been discovered after the visa was issued.

Some students could have had four-year student visas, but had dropped out of school and were trying to return on the student visa.

"It doesn't mean our visa system broke down there at all," he said. Names of students who were turned away will be on watch lists so they will be stopped if they try to enter the country again.