Clackamas County officials say investigators looking into a report of tampering by an election worker have so far found only one or two ballots that were filled in where a voter hadn't made a choice.
But the county's legal counsel, Scot Sideras, said Monday officials are looking through other ballots the worker handled to see if the tampering was more widespread. The worker hasn't been identified.
Clackamas County commissioners met Monday seeking information about the possibility of a scandal in Oregon's all-mail balloting.
The investigation raised the possibility that tampering could affect the results of local races, where voters frequently leave blanks.
Clackamas has crucial legislative races, as the two parties try to break a state House deadlock, and sharp divisions in the county commission races have drawn wide attention.