(CNN) — Federal authorities are investigating the possible arson of a ballot box in Boston after the Massachusetts Secretary of State’s office notified them of the incident, officials said.

Firefighters responded to a call about the fire just after 4 a.m. Sunday at the Boston Public Library’s main branch in Copley Square, the Boston Police Department said in a statement. Firefighters put out the blaze by filling the box with water.

The Boston Elections Department said on Twitter that 87 of the 122 ballots inside the box were “legible and able to be processed.” The department said it last picked up ballots from the box on Saturday afternoon and will mail new ballots to all voters whose ballots were identified as being in that drop box at that time.

Boston Mayor Marty Walsh and Massachusetts Secretary of State William Galvin called the incident “a disgrace to democracy, a disrespect to the voters fulfilling their civic duty, and a crime.”

“Our first and foremost priority is maintaining the integrity of our elections process and ensuring transparency and trust with our voters, and any effort to undermine or tamper with that process must be prosecuted to the fullest extent of the law,” they said in a joint statement.

Massachusetts US Attorney Andrew Lelling and FBI Special Agent in Charge Joseph Bonavolonta issued a joint statement that said federal officials were investigating the incident.

“For the next several weeks, it is a top priority of our offices to help maintain the integrity of the election process in Massachusetts by aggressively enforcing federal election laws,” the statement said, adding that members of the public should report any suspicious, election-related activity to authorities.

The elections department said all ballot boxes in Boston are under 24-hour surveillance and emptied on a daily basis. Ballots collected are brought to the department to be counted on election night with each voter’s precincts.

Any Boston voter who deposited their ballot at the box in Copley Square between 2:30 p.m. ET on Saturday, October 24, and about 4 a.m. on Sunday, October 25, should check the status of their ballot by calling the elections department at 617-635-2211.

The Boston incident isn’t the first in this election. CNN affiliate KABC last week reported that someone intentionally set fire to a ballot box in Baldwin Park, California, on October 18.

It’s not clear how may ballots were lost in that incident.

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