Kaiser High School Principal John Sosa retired at the end of the year, three months after the state Department of Education placed him on leave as it conducted an internal investigation.

Sosa, who had led the Hawaii Kai high school since 2008, was placed on paid leave in late September, but DOE officials said at the time that the department could not comment on any details of the investigation.

The following month, Kaiser employees said privately that two other employees in the school’s office had been placed on leave and that files were seized — details that the DOE also said it could not confirm at the time.

A DOE spokeswoman said Wednesday that the investigation is still underway and that the department is looking to fill the principal position permanently.

Justin Mew, principal of neighboring Niu Valley Middle School, has been filling in as interim principal.

Sosa last year was named Principal of the Year by the Hawaii Association of Secondary School Administrators, and nominated for its national counterpart’s Principal of the Year award for 2014.