Hales sought the clearance in his role as police commissioner to supervise Portland officers working with the task force. Spokesman Dana Haynes said he didn't know why clearance was denied.
Portland officers worked with the task force on a least one case of suspected domestic terrorism in the past year, Police Chief Mike Reese said in his annual report on police involvement with the task force. Police passed along a tip to federal investigators, The Oregonian reported Friday.
Portland pulled out of the FBI-led task force in 2005 but the city council reversed that decision in 2011 to allow officers to work with the task force as needed.
Reese, the assistant chief of investigations, the lieutenant of the Criminal Intelligence Unit and all officers assigned to the unit have been granted "secret" clearance by the FBI. One member is in the final step of obtaining his clearance.
Secret clearance is a step down from "top secret secure" clearance, which would allow Portland officers unescorted access to FBI offices or access to informants. The FBI informed the Portland police that they would not need to access FBI offices unescorted or informant source information.
Though the mayor was denied the secret clearance, he met with the FBI's special agent in charge twice last year.
Hales has not reapplied for the clearance and is waiting to meet the new special agent in charge, who starts at the end of this month, Haynes said.
Dave Woboril, senior deputy city attorney, has reported to the chief that the Police Bureau is in full compliance with Oregon law and the city's resolution regarding its involvement with the federal task force. Officers have only worked on investigations of suspected terrorism "that had a criminal nexus," Reese wrote in his report.