Now they will go through in the hope of being able to contact affected voters, according to the authorities in Clark County in the state of Washington.
An unknown number of ballots were completely burned when an unknown perpetrator set off a firebomb on the container.
Another ballot box in Portland, Oregon was subjected to a similar attack on Monday and a ballot box in Vancouver, Washington earlier in October. All the firebombs had the words "Free Gaza" written on them, according to sources for ABC News and The New York Times.
The actions, which are being investigated by, among others, the FBI, have been called an "attack on democracy" ahead of next week's highly contested presidential election.
"There is no doubt about it, an attack on a ballot box is an attack on our democracy and completely unacceptable", said LaVonne Griffin-Valade, the highest authority for the electoral process in the state of Oregon, in a statement.
No one has yet been arrested for the fires.
