The dean of Carnegie Mellon's H. John Heinz III School of Public Policy and Management resigned suddenly last week after the discovery of what the university referred to as "an error in judgment."

Mark Wessel

In an e-mail sent to students Friday afternoon, the university announced the resignation of Mark Wessel, who joined the Heinz School in 1993, was appointed interim dean in February 2003 and has served as permanent dean since April 2004.

The error in judgment involved "the approval of excessive transfer credits and excessive units for independent study in lieu of coursework" for a student who received a master's degree in 2004, according to the e-mail sent to students.

The administration learned of the irregularities involving the degree on Wednesday. Citing federal privacy laws, the university is not releasing any information about the student who received the degree.

CMU President Jared Cohon informed Heinz school faculty about Mr. Wessel's resignation at a 4:30 meeting Friday afternoon, said university spokesman Ken Walters. Students received an e-mail shortly afterward.

The university is reviewing records for degrees awarded in the last five years to determine whether any other degrees were awarded improperly.

"We always take any issue regarding academic integrity very seriously," said Mr. Walters. "This is something where, when we find out something like this, we review it immediately."

A phone message left at Mr. Wessel's home was not immediately returned.