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Federal authorities are investigating fires at two ballot drop boxes reported Monday morning in the Portland, Oregon, area.

Police responded to a call about a fire in Portland around 3:30 a.m. Monday, the Portland Police Bureau said in a statement. An “incendiary device” was placed in the box and security personnel extinguished the fire, officials said.

Federal officials are investigating the incident in Portland and a second fire in nearby Vancouver, Washington, with help from state and local law enforcement, said Steve Bernd, a spokesman for the FBI's Seattle office.

Nearly all of the ballots were protected by fire extinguisher in the box, but three were damaged, Multnomah County elections director Tim Scott said in a statement.

Officials plan to contact the three affected voters “via unique identifiers on their ballot envelopes so they can receive replacement ballots.” Voters who dropped off their ballots at the polls between 3:30 p.m. Saturday and 3 p.m. Monday should contact the Multnomah County Elections Division with any concerns, Scott said.

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

According to the Vancouver Police Department, the second ballot box was set on fire at a bus station in Vancouver early Monday morning. When officers arrived, they found a “suspicious device” next to the box that was smoking and on fire, police said.

The Clark County elections office said hundreds of ballots were damaged at the ballot box at the C-TRAN Park and Ride at Fisher's Landing Transit Center. This was reported by CNN affiliate KPTV.

Laura Shepard, a spokesperson for the City of Vancouver, said election officials would ask anyone who placed a ballot in the ballot box after 11 a.m. Saturday to contact them to check the status of their ballot.

Washington Secretary of State Steve Hobbs condemned the fire and confirmed that some ballots were damaged.

“We take the safety of our poll workers seriously and will not tolerate threats or acts of violence intended to undermine the democratic process,” Hobbs said.

“I strongly condemn any acts of terrorism intended to disrupt lawful and fair elections in Washington state,” Hobbs added. “Despite this incident, I have full confidence in the ability of our county election officials to keep Washington’s elections safe and secure for all voters.”

The boxes are about 15 miles apart. The Vancouver race is in Washington's 3rd Congressional District, home to one of the most competitive House races in the country.

The district is represented by Rep. Marie Gluesenkamp Perez, one of five seats held by Democrats in a district won by former President Donald Trump in 2020. She faces a rematch against Republican Joe Kent, a retired Green Beret who had Trump's support.

More fires impacting ballots have been reported recently across the country. Last week, a mailbox outside a Phoenix post office was set on fire, damaging an unknown number of ballots. A 35-year-old man has been charged with arson in connection with the incident. Phoenix police said he told them it was not politically motivated.

The fires came after the FBI and Department of Homeland Security recently issued a bulletin raising concerns that “election-related grievances” such as belief in voter fraud could motivate domestic extremists to commit violence in the weeks before and after the November election .

In the intelligence bulletin obtained by CNN, authorities said some domestic violent extremists likely view publicly accessible locations, including ballot drop boxes, as “attractive targets.”