Authorities in Oregon and Washington state have identified a "suspect vehicle" they say is connected to incendiary devices that caused fires at ballot boxes in both states.

The Portland Police Bureau (PPB) released two surveillance photos of a black or dark-colored Volvo S-60 they believe is connected to the ballot box fires. The vehicle does not have a front license plate, but it does have an unknown rear plate, police added. 

Three ballots were destroyed in a fire at a ballot box in Portland, Oregon, on Monday morning. A few hours later, hundreds of ballots were destroyed in a fire at a drop box in nearby Vancouver, Washington. 

Both ballot boxes were equipped with fire suppression systems, but the system inside the ballot box in Vancouver failed, causing more ballots to be destroyed.

'INCENDIARY DEVICE' SPARKS FIRE AT PORTLAND, OREGON BALLOT BOX

Image of suspected ballot box arsonist vehicle

The Portland Police Bureau released images of the suspect vehicle that is believed to be connected to ballot box fires in Portland and Vancouver. (Portland Police Bureau)

Police said the incendiary devices were placed on the outside of the boxes. 

During a press conference on Monday, authorities said they were able to recover enough material from the devices to show that the two fires were connected. They also said the incidents were connected to an Oct. 8 incident in which an incendiary device was placed at a different ballot box in Vancouver.

"We don’t know the motive behind these acts," PPB Assistant Chief Amanda McMillan said. "We do know acts like this are targeted, and they're intentional, and we’re concerned about that intentional act trying to impact the election process. We’re dedicated to stopping this kind of behavior."

ARIZONA ELECTION BALLOTS DAMAGED AFTER USPS MAILBOX LIT ON FIRE, SUSPECT ARRESTED

Portland ballot box fire

A ballot box is seen damaged in Portland, Ore., on Monday, Oct. 28 following a fire, police say. (Portland Police Bureau)

Greg Kimsey, the longtime elected auditor in Clark County, Washington, which includes Vancouver, urged voters who dropped their ballots in the transit center box after 11 a.m. Saturday to contact his office for a replacement ballot.

"Heartbreaking," Kimsey said. "It’s a direct attack on democracy."

Kimsey said police will increase patrols around ballot drop box locations and Clark County Elections Office employees will observe ballot boxes 24 hours a day, seven days a week until the election is over.

He said employees will not confront anyone, but will instead contact police if they spot anything suspicious.

Vancouver is the biggest city in Washington’s 3rd Congressional District, the site of what is expected to be one of the closest U.S. House races in the country, between first-term Democratic Rep. Marie Gluesenkamp Perez and Republican challenger Joe Kent.

Alleged arson suspect vehicle

Police released photos of a suspected vehicle allegedly involved in ballot box fires in Vancouver and Portland. (KPTV)

The Portland FBI also released a statement regarding the arson and said they are actively investigating both situations.

"The FBI is coordinating with federal, state and local partners to actively investigate the two incidents in Vancouver, Washington, and Portland, Oregon, in the early morning hours of Monday, October 28th to determine who is responsible," the statement read. 

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The FBI is encouraging anyone with information to contact the nearest FBI office, provide information through tips.fbi.gov or call 1-800-225-5324.

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These latest incidents come just days after roughly 20 mail-in ballots were damaged when a U.S. Postal Service mailbox was lit on fire in Phoenix.

The suspect in the Arizona arson case, Dieter Klofkorn, 35, has since been arrested on one felony count of Arson to Property. 

Fox News Digital's Greg Norman and The Associated Press contributed to this report.