US authorities investigating two ballot box fires

US authorities are investigating after at least two ballot boxes were set on fire.

Police responded to a call about a fire in Portland about 3.30am Monday (11.30pm Monday NZT), the Portland Police Bureau said in a statement. An "incendiary device" was placed inside the box and security personnel extinguished the fire, officials said.

CNN has reached out to Multnomah County Elections office for comment.

A second ballot box was set on fire early Monday morning at a bus station in nearby Vancouver, Washington, CNN affiliate KPTV reported. The Clark County Elections Office said hundreds of ballots were damaged at the box in the C-TRAN Park and Ride at Fisher's Landing Transit Centre, KPTV reported.

- CNN