Voters in two counties in Washington state and Oregon have not received mail-in ballots with less than a week to go before the election, election officials said Wednesday. The news comes two days after incendiary devices were set off in ballot drop boxes in both those states.

The U.S. Postal Service failed to deliver an unknown number of ballots in Coos County, Oregon, and it didn’t deliver up to 300 ballots in Whitman County, Washington, elections officials told The Associated Press. Both states conduct elections by mail.

In Coos County, a rural, coastal area in Oregon’s southwest corner, the number of missing ballots wasn’t clear because officials only know of a missing ballot if the voter tells them, Laura Kerns, a spokesperson for the Oregon Secretary of State’s office, said in an email Wednesday. Coos County has about 50,000 active voters.

In Washington, up to 300 ballots have not been delivered in the community of Garfield, Whitman County Auditor Sandy Jamison said. The town about is about 55 miles (88 kilometers) southeast of Spokane, in the eastern part of the state. There have also been some reports of missing ballots outside the town, Jamison said.

Coos County Clerk Julie Brecke said in a statement that her office has been inundated with calls after the ballots didn’t arrive “as a result of an error at USPS.”

Officials with the postal service did not immediately return messages to The Associated Press on Wednesday. U.S. Postmaster General Louis DeJoy has repeatedly sought to reassure Americans that the Postal Service is prepared to meet the challenge of mail-in ballots.

Some election officials remain wary based on their experience during the primary season, when some ballots arrived late or without the postmarks required by some state laws.

DeJoy acknowledged that a massive network reorganization caused temporary problems, but he assured election officials that changes are being paused until after the election. “We engage in heroic efforts intended to beat the clock,” DeJoy told reporters last month.

Postal Service officials said that nearly 98% of ballots were returned to election officials within three days and that 99.9% of ballots were delivered within seven days in the last presidential election - at the height of the pandemic in 2020.

In Whitman County, Jamison has verified that a third-party vendor delivered about 24,000 ballots to the post office Oct. 16 and the postal service marked them all - including the now missing ones - as received, Jamison said.

“I don’t know where they went after that,” she said.

Postal officials told her Wednesday they were still investigating. “They still have no official word to me that they have found the ballots,” Jamison said.

″We’re reissuing ballots as a quick turnaround as we can get, as time is of the essence now, obviously, for them to get their ballots back into us,” she said. Ballots must be postmarked by Nov. 5.

Residents have the option of having their replacement ballot mailed to them or they can pick it up in her office.

In Oregon, officials also are encouraging people to contact the Coos County clerk’s office as soon as possible to get a replacement ballot issued.

Kerns said the problem appears isolated to Coos County.

Any ballot postmarked by the U.S. Postal Service on or before Nov. 5 will be counted, even if it is received in the clerk’s office up to seven days later, Kerns said.

In a statement, the Oregon state Senate Republican Caucus urged the secretary of state, county election officials and the postal service “to immediately resolve this unacceptable delay and ensure every voter receives their ballot without further interference.”

Attacks on ballot boxes in both states were also reported earlier this week.

On Monday, incendiary devices were set off at two ballot drop boxes - one in Portland, Oregon, and another in nearby Vancouver, Washington - destroying hundreds of ballots.