An employee at Oregon's tax collection agency copied the data of 36,000 people, including social security numbers, and stored the files to a personal account, the state announced on Friday.

The Department of Revenue detected the breach on Feb. 23 and moved quickly to remove the files from the employee's cloud account, according to a news release. But officials waited a month to disclose the news because it took that long to identify how many people were affected, spokeswoman Joy Krawczyk said.

There was no evidence that anyone other than the state employee viewed or otherwise accessed the files, according to the state.

It was unclear why the employee copied the information, because Krawczyk said the department cannot disclose any explanation the man might have provided until it finishes an investigation. However, she said, based on the volume of the data it didn't appear to be an accident.

"The employee is entitled to due process for employment related matters and we need to let that process finish before releasing any information about it," Krawczyk said.

The data breach did not include taxpayers' bank account information, because the files were related to a list of individuals who paid their taxes using checks and turned out to have insufficient funds. "It is a bit puzzling why it was this specific information," Krawczyk said.

The tax agency may require additional identity validation from affected taxpayers when they file their returns this year, and the state will provide identity theft recovery services to them.

-- Hillary Borrud

503-294-4034; @hborrud