Ballot drop boxes in Portland, Oregon, and neighboring Vancouver, Washington, were set on fire early Monday morning, just over a week before Election Day, according to police. Local officials reported that three ballots were damaged in Portland, while potentially “hundreds” were affected in Vancouver.

The Portland Police Bureau stated that an “incendiary device” was placed inside a sidewalk ballot box in the Central City district. By the time officers arrived around 3:30 a.m. local time, security personnel had already extinguished the fire.

“Officers determined an incendiary device was placed inside the ballot box and used to ignite the fire,” the Portland police said in a statement, adding that the bureau’s Explosive Disposal Unit removed the device. The investigation into the incident is ongoing.

A statement from the Multnomah County election office indicated that “fire suppressant inside the ballot box protected virtually all the ballots.”

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

At around 4 a.m. local time, about half an hour after the fire in Portland, police in Vancouver responded to another ballot box fire. Flames and smoke were reported coming from the box near the Fisher’s Landing Transit Depot, according to NBC News affiliate KGW in Portland.

Vancouver police stated that officers arrived to find smoke and flames and discovered a “suspicious device” next to the box. The fire was extinguished, and the city’s Metro Explosive Disposal Unit collected the device.

The FBI is investigating the incidents, but no further details are currently available, according to Vancouver police. Clark County auditor Greg Kimsey noted that potentially “hundreds” of ballots could be affected and advised anyone who submitted a ballot after 11 a.m. on Saturday to contact the office to check on their ballot’s status.

It remains unclear whether the two fires are connected. Earlier this month, the Vancouver bomb squad responded to a report of a “suspicious device” near a downtown ballot box, which was “safely removed,” and the ballot box itself was confirmed to be “not compromised.”

Vancouver is located in Washington’s 3rd Congressional District, where Democratic Rep. Marie Gluesenkamp Perez is competing against Donald Trump-backed Republican challenger Joe Kent in a closely watched House race.

Several ballots were also damaged in Phoenix last week when a U.S. Postal Service mailbox was set on fire. Police arrested a suspect who admitted to committing arson but stated that the incident was not politically motivated.