With just days until Election Day, hundreds of ballots were destroyed by fires this week at two ballot drop boxes in the Pacific Northwest, and investigators are searching for a culprit they say is responsible for both.

Many of the ballots in a drop box in Portland were unaffected, but hundreds of ballots were destroyed in a second ballot box fire in nearby Vancouver, Washington, election officials said. The incidents are believed to be related to a third incident earlier this month in Vancouver.

The incidents come as a US Department of Homeland Security bulletin from September obtained by the watchdog group Property of the People warned, “Some social media users are discussing and encouraging various methods of sabotaging ballot drop boxes and avoiding detection, likely heightening the potential for targeting of this election infrastructure through the 2024 election cycle.

“Election infrastructure remains an attractive target for some domestic violent extremists and other threat actors with election-related grievances who seek to disrupt the democratic process and election operations,” the bulletin warned.

“Make no mistake, an attack on a ballot box is an attack on our democracy and completely unacceptable,” Oregon Secretary of State LaVonne Griffin-Valade said Monday. “Whatever the motivation behind this incident, there is no justification for any attempt to disenfranchise voters.”

“We take the safety of our election workers seriously and will not tolerate threats or acts of violence that seek to undermine the democratic process,” said Washington Secretary of State Steve Hobbs.

“I strongly denounce any acts of terror that aim to disrupt lawful and fair elections in Washington state.”

Here’s what we know:

How the ballot boxes went up in flames

An “incendiary device” was attached to the side of a ballot drop box when Portland Police responded about 3:30 a.m. Monday, and security personnel extinguished the fire, the Portland Police Bureau said in a statement.

At a bus station in Vancouver, Washington, just 15 miles away, a second ballot box was set on fire early Monday, according to the Vancouver Police Department. Responding officers discovered a “suspicious device” smoking and on fire next to the box, police said.

All ballot boxes in Multnomah County and Clark County have fire suppressant installed, election officials said during a news conference Monday. Multnomah County Elections Director Tim Scott said fire suppressant inside the Portland box protected more than 400 ballots inside, and only three ballots were damaged.

Election officials were still counting all the ballots involved in the Vancouver fire, but believe hundreds of ballots were destroyed, said Clark County Auditor Greg Kimsey.

Voting in Oregon and Washington is done almost entirely by mail or ballot drop off. Less than 1% of people in Multnomah County vote in person, according to Scott. In Clark County, 60% of the ballots received are from ballot drop boxes, Kimsey said.

“Drop boxes are useful and secure ways voters can return their mail ballot without using the US Postal Service,” Jay Riestenberg, director of communications for Voting Rights Lab said. “They help cut down on ballots returned by mail, which can alleviate the stress put on the US Postal Service and local election officials during busy election seasons.”

But according to Voting Rights Lab, drop boxes have come under scrutiny by politicians and election officials, and 12 states have enacted bills banning or restricting drop boxes, half of which outright ban them.

What should I do if my ballot was impacted?

John Burnside and his wife voted Sunday afternoon by depositing their ballots in a drop box near their Vancouver, Washington, home.

The next day, he saw reports that someone set fire to the box, destroying hundreds of votes.

“When I saw the video of them scraping the ballots out of there. I knew there was little chance that mine would have been working,” Burnside told CNN. “I don’t know that they were able to salvage any of the ballots out of that box.”

They’ve used that drop box in past elections, Burnside said, and it was disturbing that someone would destroy it.

“Our world has changed, and things that you may have taken for granted as secure in the past, you have to rethink,” he said.

Burnside said he looked online and saw their ballots had not been received, so they immediately ordered replacement ballots. This time, he said, they’ll drive across town to the election office so they can deliver their votes in person.

“It’s probably a 20-minute drive, but it’s well worth it at this point,” Burnside said.

Laura Shepard, a spokesperson for the city of Vancouver, said election officials are asking anyone who may have placed a ballot in the box after 11 a.m. on Saturday to contact them to check the status of their ballot.

“Voters should be assured that even if their ballots were in the affected box, their votes will be counted,” Scott said.

Officials in Portland plan to contact the three affected voters using “unique identifiers on their ballot envelopes, so they can receive replacement ballots,” according to Scott.

Authorities looking for ‘suspect vehicle’

Evidence from the incendiary devices found at the ballot boxes Monday shows the fires are connected to each other, as well as to a third incident October 8, when an incendiary device was placed at a different drop box in Vancouver, said Portland Police Bureau spokesperson Mike Benner.

“We don’t know the motives behind these acts – sounds like a series of three at this point – but we do know that acts like this are targeted and intentional,” Portland Police Bureau Assistant Chief Amanda McMillan said. “We are concerned about that intentional act trying to affect the election process.”

Police identified a “suspect vehicle” seen leaving the scene of the fire in Portland, they said in a news release Monday – a black or dark-colored 2001-2004 Volvo S-60.

According to the Oregon Department of Driver and Motor Vehicle Services, 3,828 of those vehicles were registered in the state – 558 of which have a valid registration status.

The FBI’s Seattle office told CNN it is working with state and local authorities on the investigation.

Enhanced ballot box security

As Election Day nears, state leaders are encouraging citizens to vote despite the incidents, pledging increased security around the drop boxes.

“There are multiple ways for voters to cast their ballot and make sure their voice is heard,” Washington Gov. Jay Inslee said.

The ballot box in Portland has already been replaced, according to Multnomah County Chair Jessica Vega Pederson, and law enforcement in Multnomah County and Vancouver, Washington, plan to increase patrols of ballot boxes in the area.

“Voter intimidation or any criminal act to undermine the upcoming election is un-American & will not be tolerated,” Oregon Gov. Tina Kotek said on X.

Inslee said in a statement Monday evening “there will be 24-hour enhanced security around ballot drop-off locations.”

Vancouver is in Washington’s 3rd Congressional District, represented by Rep. Marie Gluesenkamp Perez, where one of the most competitive House races in the country is taking place.

Following the ballot box fires, Gluesenkamp Perez requested overnight law enforcement patrols at drop boxes through Election Day.

The Democrat congresswoman told CNN’s Kaitlan Collins she isn’t angry about the damaged ballots for partisan reasons, but “because I’m an American who sees the corrosive and toxic environment that we’ve seen across the country come home in a really damaging and ugly way.”

CNN’s Nicole Chavez, Taylor Romine and David Williams contributed to this report.