American University student government leaders said yesterday that they are very concerned about an investigation into suspended President Benjamin A. Ladner's expenses and are seeking assurance from school administrators that their tuition has not been misspent.

Officials of the student government said they would not issue a formal statement about the board of trustees' probe of Ladner and more than $500,000 in expenses, but they said they were in discussions with top school officials.

"When it comes to students' money being spent inappropriately or allegations of such, we take it seriously, very seriously," said Joseph Vidulich, 19, a sophomore and secretary of the student government, adding that students want to give Ladner "the benefit of the doubt." But, he said, referring to a trustee's allegation that Ladner spent more than $22,000 on a first-class plane ticket, "If he was spending as much money as tuition to fly to Nigeria, that is a serious problem and something we need to fix."

Zach Ulrich, 20, a junior and comptroller of the student government, said students were concerned that the investigation would hurt the university, which, under Ladner, has tightened academic standards and gone up in national rankings.

"It would be a shame to see something like that mar those efforts," Ulrich said.

One mother of a junior at the private Northwest Washington university complained that the school had not formally notified parents that Ladner was placed on administrative leave in August. She said parents had a right to be told about the situation at the school, where undergraduate tuition is nearly $28,000 a year.

"The president of the college is suspended since Aug. 24 and I don't have a communication from the school?" Sheryl Garrett of Southern California said.

Garrett said she called the school yesterday but nobody would tell her who was acting president. Provost Cornelius M. Kerwin has taken that post.

David Taylor, chief of staff to the president, cited the administration's numerous postings about the situation on the university's Web site.

The "president's welcome" on the site has a message from Ladner but no mention of his leave, and a biography of Kerwin describes him as provost. But postings elsewhere on the site mention Kerwin's role as acting president, and some alumni said they were told of the situation.

Some were confident that Ladner would be back soon. Others were reserving judgment.

"It seems unfortunate," said Jason Liechty of Chicago, who graduated in 1998, but the situation doesn't change how he feels about AU. "It's not like he's [Ladner] synonymous with the school."

Allyson Berman, who graduated in 1999, said, "Whatever happens, AU's going to be just fine. . . . I think there are a lot of good things going on at American," such as the new arts complex.

Anthony Ahrens, chairman of the faculty senate, said, "I think there is great concern on the part of the faculty," and he is consulting with the faculty senate about its response.

Several faculty members, who spoke anonymously because they feared for their positions, said some professors have been quietly talking about how to stage a group protest or register their concern without endangering anybody's job.

Special correspondent Ed O'Keefe contributed to this report.