ALTON, Ill. – Southern Illinois University’s dental school has suspended the grades of all 52 first-year students while it investigates them for possible academic misconduct, university officials said.

Officials on Wednesday would not discuss details of the suspected wrongdoing, and stopped short of saying the students cheated at the School of Dental Medicine in this Mississippi River city northeast of St. Louis.

The issue surfaced in May, when “there was some question about the academic integrity of our first-year students” at the four-year school, university spokesman Greg Conroy said.

The matter was forwarded to the school’s conduct committee, a faculty panel that reviews allegations of student misconduct. The school’s dean, Ann Boyle, then will review the committee’s recommendation and take any action, with possible penalties ranging from a warning to expulsion.

“We feel we owe it to the program and the students to do a thorough investigation,” said Conroy, who could not say how long the inquiry might take. “It’s going to take a certain amount of time to interview all 52 students,” many of them now away on summer break.

In a brief statement, Boyle said only that “this matter raises questions about the integrity and ethical behavior of Year I students and is, therefore, under investigation.”

“Personal integrity and ethical standards form the foundation of all health care professions, including dentistry,” she said.

Calls to Boyle’s office Wednesday were referred to Conroy, who said all 52 students would be allowed to enroll in and attend fall classes “without losing any time,” pending the outcome of the investigation.

An unsigned letter sent to local media purporting to be from the dental school’s first-year class called the investigation “nothing more than a witch hunt,” and said it involved student advisers who apparently shared with first-year students tests from previous years.

According to the letter, which includes the typed names of all 52 affected students but no signatures, the practice has gone on for at least two decades as a legitimate way to understand how each teacher tests.

The letter also says that Boyle “charges that this sharing of notes is considered cheating and that any student who did not report the trading of test file information contained in these intra-class e-mails was condoning cheating within the class.”

The letter claims that the university never told students how they violated university rules, preventing them from preparing a proper defense. According to the letter, the suspect work could range from cheating to theft of university property to misuse of documents.

“There is absolutely no evidence that suggests that students stole university property, cheated by any means, acted unprofessionally or were involved in misconduct of any kind,” according to the letter.

The letter said that, by suspending their grades, the school has put the students’ academic careers in limbo and cost them offers for scholarships that require full transcripts.

“Grades must be released and research must continue immediately until this investigation is concluded,” the letter read, adding that students were being interviewed without legal representation.

Conroy said each student has been given a file containing the allegations and can show that to an attorney for feedback, though students are allowed to bring an adviser from the faculty _ not a lawyer _ with them for their committee hearing.

Messages left by The Associated Press Wednesday for several other people named in the letter were not immediately returned.

On its Web site, the school boasts that “historically, students from the SIU dental school score high nationally on the National Board Dental Exams, Parts I and II.” Passing the exams _ a requirement for licensure _ “is a strong indicator of student preparedness to practice dentistry.”